diff --git a/.github/workflows/werror.yml b/.github/workflows/werror.yml
index 152d6e89d..751a9847e 100644
--- a/.github/workflows/werror.yml
+++ b/.github/workflows/werror.yml
@@ -8,7 +8,7 @@ on:
 
 env:
   _R_CHECK_FORCE_SUGGESTS_: "false"
-  RCPP_CXXFLAGS: "-Werror -Wall -Wextra"
+  RCPP_CXXFLAGS: "-Werror -Wall -Wextra -Wconversion"
 
 jobs:
   ci:
diff --git a/ChangeLog b/ChangeLog
index ae20b532b..cb582cc3f 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,50 @@
+2026-09-05  Iñaki Ucar <iucar@fedoraproject.org>
+
+	* .github/workflows/werror.yaml: Add -Wconversion
+
+	* inst/include/Rcpp/macros/interface.h: Mark GenericProxy constructor as
+	explicit to resolve ambiguities with validated SEXP constructors
+	* inst/include/Rcpp/vector/Vector.h: Idem
+	* inst/include/Rcpp/DataFrame.h: Idem with ad hoc constructor
+	* inst/include/Rcpp/vector/ListOf.h: In this case, the implicit conversion
+	of ListOf<T> e.g. from List is intentional, so the previously generic
+	constructor now gets restricted to cases that are convertible to SEXP
+
+	* inst/include/Rcpp/stats/dpq/dpq.h: Expand and homogenize R_xlen_t use
+	* inst/include/Rcpp/sugar/functions/head.h: Idem
+	* inst/include/Rcpp/vector/MatrixColumn.h: Idem
+	* inst/include/Rcpp/vector/MatrixRow.h: Idem
+	* inst/include/Rcpp/vector/RangeIndexer.h: Idem
+	* inst/include/Rcpp/internal/wrap.h: Idem and fix potential integer overflow
+	* inst/include/Rcpp/sugar/operators/Comparator_With_One_Value.h: Idem and
+	fix a bug where rhs_is_na may return NaN instead of NA_INTEGER
+	* inst/include/Rcpp/Language.h: Revert incorrect use of R_xlen_t
+	* inst/include/Rcpp/vector/SubMatrix.h: Idem, because Matrix rows and cols
+	are restricted to int anyway
+
+	* src/date.cpp: Add missing explicit integer narrowing
+	* inst/tinytest/cpp/dates.cpp: Add static_cast to time_t
+	* inst/tinytest/cpp/language.cpp: Fix implicit cast to int
+	* inst/tinytest/cpp/Matrix.cpp: Idem
+	* inst/tinytest/cpp/Module.cpp: Idem
+	* inst/tinytest/cpp/String.cpp: Idem
+	* inst/tinytest/cpp/Vector.cpp: Idem
+	* inst/include/Rcpp/vector/Matrix.h: Idem
+	* inst/include/Rcpp/vector/Vector.h: Idem
+	* inst/include/Rcpp/sugar/Range.h: Idem
+	* inst/include/Rcpp/sugar/functions/seq_along.h: Idem
+	* inst/include/Rcpp/sugar/functions/rowSums.h: Idem
+	* inst/include/Rcpp/sugar/functions/sample.h: Idem
+	* inst/include/Rcpp/sugar/matrix/col.h: Idem
+	* inst/include/Rcpp/sugar/matrix/diag.h: Idem
+	* inst/include/Rcpp/sugar/matrix/lower_tri.h: Idem
+	* inst/include/Rcpp/sugar/matrix/outer.h: Idem
+	* inst/include/Rcpp/sugar/matrix/row.h: Idem
+	* inst/include/Rcpp/sugar/matrix/upper_tri.h: Idem
+	* inst/include/Rcpp/sugar/functions/var.h: Add static_cast to double
+	* inst/include/Rcpp/vector/Subsetter.h: Add several necessary static_cast
+	* inst/include/Rcpp/vector/MatrixBase.h: Idem
+
 2026-09-04  Dirk Eddelbuettel  <edd@debian.org>
 
 	* DESCRIPTION (Version, Date): Roll micro version and date
diff --git a/inst/include/Rcpp/DataFrame.h b/inst/include/Rcpp/DataFrame.h
index 65a81576f..e93a05d1b 100644
--- a/inst/include/Rcpp/DataFrame.h
+++ b/inst/include/Rcpp/DataFrame.h
@@ -1,7 +1,8 @@
 
 // DataFrame.h: Rcpp R/C++ interface class library -- data frames
 //
-// Copyright (C) 2010 - 2026  Dirk Eddelbuettel and Romain Francois
+// Copyright (C) 2010 - 2025  Dirk Eddelbuettel and Romain Francois
+// Copyright (C) 2026         Dirk Eddelbuettel, Romain Francois and Iñaki Ucar
 //
 // This file is part of Rcpp.
 //
@@ -46,7 +47,8 @@ namespace Rcpp{
             set__(other) ;
         }
 
-        template <typename T>
+        template <typename T,
+                  typename std::enable_if<std::is_convertible<T, SEXP>::value, int>::type = 0>
         DataFrame_Impl( const T& obj ) ;
 
         DataFrame_Impl& operator=( DataFrame_Impl& other){
diff --git a/inst/include/Rcpp/Language.h b/inst/include/Rcpp/Language.h
index d893df67a..88df9544f 100644
--- a/inst/include/Rcpp/Language.h
+++ b/inst/include/Rcpp/Language.h
@@ -2,6 +2,7 @@
 // Language.h: Rcpp R/C++ interface class library -- language objects (calls)
 //
 // Copyright (C) 2010 - 2025 Dirk Eddelbuettel and Romain Francois
+// Copyright (C) 2026        Dirk Eddelbuettel, Romain Francois and Iñaki Ucar
 //
 // This file is part of Rcpp.
 //
@@ -189,7 +190,7 @@ namespace Rcpp{
         class unary_call : public std::function<RESULT_TYPE(T)> {
     public:
         unary_call( Language call_ ) : call(call_), proxy(call_,1) {}
-        unary_call( Language call_, R_xlen_t index ) : call(call_), proxy(call_,index){}
+        unary_call( Language call_, int index ) : call(call_), proxy(call_,index){}
         unary_call( Function fun ) : call( fun, R_NilValue), proxy(call,1) {}
 
         RESULT_TYPE operator()( const T& object ){
@@ -206,7 +207,7 @@ namespace Rcpp{
         class binary_call : public std::function<RESULT_TYPE(T1,T2)> {
     public:
         binary_call( Language call_ ) : call(call_), proxy1(call_,1), proxy2(call_,2) {}
-        binary_call( Language call_, R_xlen_t index1, R_xlen_t index2 ) : call(call_), proxy1(call_,index1), proxy2(call_,index2){}
+        binary_call( Language call_, int index1, int index2 ) : call(call_), proxy1(call_,index1), proxy2(call_,index2){}
         binary_call( Function fun) : call(fun, R_NilValue, R_NilValue), proxy1(call,1), proxy2(call,2){}
 
         RESULT_TYPE operator()( const T1& o1, const T2& o2 ){
diff --git a/inst/include/Rcpp/api/meat/DataFrame.h b/inst/include/Rcpp/api/meat/DataFrame.h
index b679e32ab..f73a297f2 100644
--- a/inst/include/Rcpp/api/meat/DataFrame.h
+++ b/inst/include/Rcpp/api/meat/DataFrame.h
@@ -1,4 +1,5 @@
-// Copyright (C) 2013 Romain Francois
+// Copyright (C) 2013 - 2025 Romain Francois
+// Copyright (C) 2026        Romain Francois and Iñaki Ucar
 //
 // This file is part of Rcpp.
 //
@@ -21,7 +22,8 @@
 namespace Rcpp{
 
      template <template <class> class StoragePolicy>
-     template <class T>
+     template <class T,
+               typename std::enable_if<std::is_convertible<T, SEXP>::value, int>::type>
      DataFrame_Impl<StoragePolicy>::DataFrame_Impl( const T& obj){
         set__(Shield<SEXP>(wrap(obj)));
      }
diff --git a/inst/include/Rcpp/internal/wrap.h b/inst/include/Rcpp/internal/wrap.h
index f9c646da4..3c5251fa2 100644
--- a/inst/include/Rcpp/internal/wrap.h
+++ b/inst/include/Rcpp/internal/wrap.h
@@ -564,7 +564,7 @@ namespace Rcpp {
 	template <typename T>
         inline SEXP wrap_dispatch_matrix_logical(const T& object, ::Rcpp::traits::true_type) {
             int nr = object.nrow(), nc = object.ncol();
-            Shield<SEXP> res(Rf_allocVector(LGLSXP, nr * nc));
+            Shield<SEXP> res(Rf_allocVector(LGLSXP, static_cast<R_xlen_t>(nr) * nc));
             int k=0;
             int* p = LOGICAL(res);
             for (int j=0; j<nc; j++)
@@ -581,7 +581,7 @@ namespace Rcpp {
         inline SEXP wrap_dispatch_matrix_primitive(const T& object) {
             const int RTYPE = ::Rcpp::traits::r_sexptype_traits<STORAGE>::rtype;
             int nr = object.nrow(), nc = object.ncol();
-            Shield<SEXP> res(Rf_allocVector(RTYPE, nr*nc));
+            Shield<SEXP> res(Rf_allocVector(RTYPE, static_cast<R_xlen_t>(nr)*nc));
 
             int k=0;
             STORAGE* p = r_vector_start< RTYPE>(res);
@@ -603,7 +603,7 @@ namespace Rcpp {
 	template <typename T>
         inline SEXP wrap_dispatch_matrix_not_logical(const T& object, ::Rcpp::traits::r_type_string_tag) {
             int nr = object.nrow(), nc = object.ncol();
-            Shield<SEXP> res(Rf_allocVector(STRSXP, nr*nc));
+            Shield<SEXP> res(Rf_allocVector(STRSXP, static_cast<R_xlen_t>(nr)*nc));
 
             int k=0;
             for (int j=0; j<nc; j++)
@@ -619,7 +619,7 @@ namespace Rcpp {
     	template <typename T>
         inline SEXP wrap_dispatch_matrix_not_logical(const T& object, ::Rcpp::traits::r_type_generic_tag) {
             int nr = object.nrow(), nc = object.ncol();
-            Shield<SEXP> res(Rf_allocVector(VECSXP, nr*nc));
+            Shield<SEXP> res(Rf_allocVector(VECSXP, static_cast<R_xlen_t>(nr)*nc));
 
             int k=0;
             for (int j=0; j<nc; j++)
@@ -665,12 +665,12 @@ namespace Rcpp {
 
 	template <typename T, typename elem_type>
         inline SEXP wrap_dispatch_importer__impl__prim(const T& object, ::Rcpp::traits::false_type) {
-            int size = object.size();
+            R_xlen_t size = object.size();
             const int RTYPE = ::Rcpp::traits::r_sexptype_traits<elem_type>::rtype;
             Shield<SEXP> x(Rf_allocVector(RTYPE, size));
             typedef typename ::Rcpp::traits::storage_type<RTYPE>::type CTYPE;
             CTYPE* start = r_vector_start<RTYPE>(x);
-            for (int i=0; i<size; i++) {
+            for (R_xlen_t i=0; i<size; i++) {
 		start[i] = object.get(i);
             }
             return x;
@@ -679,12 +679,12 @@ namespace Rcpp {
 
     	template <typename T, typename elem_type>
     	inline SEXP wrap_dispatch_importer__impl__prim(const T& object, ::Rcpp::traits::true_type) {
-            int size = object.size();
+            R_xlen_t size = object.size();
             const int RTYPE = ::Rcpp::traits::r_sexptype_traits<elem_type>::rtype;
             Shield<SEXP> x(Rf_allocVector(RTYPE, size));
             typedef typename ::Rcpp::traits::storage_type<RTYPE>::type CTYPE;
             CTYPE* start = r_vector_start<RTYPE>(x);
-            for (int i=0; i<size; i++) {
+            for (R_xlen_t i=0; i<size; i++) {
 		start[i] = caster<elem_type,CTYPE>(object.get(i));
             }
             return x;
@@ -698,9 +698,9 @@ namespace Rcpp {
 
 	template <typename T, typename elem_type>
         inline SEXP wrap_dispatch_importer__impl(const T& object, ::Rcpp::traits::r_type_string_tag) {
-            int size = object.size();
+            R_xlen_t size = object.size();
             Shield<SEXP> x(Rf_allocVector(STRSXP, size));
-            for (int i=0; i<size; i++) {
+            for (R_xlen_t i=0; i<size; i++) {
 		SET_STRING_ELT(x, i, make_charsexp(object.get(i)));
             }
             return x;
@@ -708,9 +708,9 @@ namespace Rcpp {
 
     	template <typename T, typename elem_type>
     	inline SEXP wrap_dispatch_importer__impl(const T& object, ::Rcpp::traits::r_type_generic_tag) {
-            int size = object.size();
+            R_xlen_t size = object.size();
             Shield<SEXP> x(Rf_allocVector(VECSXP, size));
-            for (int i=0; i<size; i++) {
+            for (R_xlen_t i=0; i<size; i++) {
 		SET_VECTOR_ELT(x, i, object.wrap(i));
             }
             return x;
diff --git a/inst/include/Rcpp/macros/interface.h b/inst/include/Rcpp/macros/interface.h
index c22598f25..3579bd0f7 100644
--- a/inst/include/Rcpp/macros/interface.h
+++ b/inst/include/Rcpp/macros/interface.h
@@ -1,4 +1,5 @@
-// Copyright (C) 2013 Romain Francois
+// Copyright (C) 2013 - 2025  Romain Francois
+// Copyright (C) 2026         Romain Francois and Iñaki Ucar
 //
 // This file is part of Rcpp.
 //
@@ -31,7 +32,7 @@ __CLASS__& operator=(const __CLASS__& rhs) {                                   \
     return Storage::copy__(rhs) ;                                              \
 }                                                                              \
 template <typename Proxy>                                                      \
-__CLASS__( const GenericProxy<Proxy>& proxy ){                                 \
+explicit __CLASS__( const GenericProxy<Proxy>& proxy ){                        \
     Storage::set__( proxy.get() ) ;                                            \
 }
 
@@ -42,7 +43,7 @@ __CLASS__& operator=(const __CLASS__& rhs) {                                   \
     return Storage::copy__(rhs) ;                                              \
 }                                                                              \
 template <typename Proxy>                                                      \
-__CLASS__( const GenericProxy<Proxy>& proxy ){                                 \
+explicit __CLASS__( const GenericProxy<Proxy>& proxy ){                        \
     Storage::set__( proxy.get() ) ;                                            \
 }
 
diff --git a/inst/include/Rcpp/stats/dpq/dpq.h b/inst/include/Rcpp/stats/dpq/dpq.h
index ea87b13dc..c5721f06f 100644
--- a/inst/include/Rcpp/stats/dpq/dpq.h
+++ b/inst/include/Rcpp/stats/dpq/dpq.h
@@ -2,7 +2,8 @@
 //
 // dpq.h: Rcpp R/C++ interface class library -- normal distribution
 //
-// Copyright (C) 2010 - 2016  Dirk Eddelbuettel and Romain Francois
+// Copyright (C) 2010 - 2025 Dirk Eddelbuettel and Romain Francois
+// Copyright (C) 2026        Dirk Eddelbuettel, Romain Francois and Iñaki Ucar
 //
 // This file is part of Rcpp.
 //
@@ -38,11 +39,11 @@ class D0 : public Rcpp::VectorBase< REALSXP, NA, D0<RTYPE,NA,T> > {
     D0( FunPtr ptr_, const VEC_TYPE& vec_, bool log_ ) :
         ptr(ptr_), vec(vec_), log(log_) {}
 
-    inline double operator[]( int i) const {
+    inline double operator[]( R_xlen_t i) const {
         return ptr( vec[i], log );
     }
 
-    inline int size() const { return vec.size(); }
+    inline R_xlen_t size() const { return vec.size(); }
 
 private:
     FunPtr ptr ;
@@ -59,11 +60,11 @@ class D1 : public Rcpp::VectorBase< REALSXP, NA, D1<RTYPE,NA,T> > {
     D1( FunPtr ptr_, const VEC_TYPE& vec_, double p0_ , bool log_) :
         ptr(ptr_), vec(vec_), p0(p0_), log(log_) {}
 
-    inline double operator[]( int i) const {
+    inline double operator[]( R_xlen_t i) const {
         return ptr( vec[i], p0, log );
     }
 
-    inline int size() const { return vec.size(); }
+    inline R_xlen_t size() const { return vec.size(); }
 
 private:
     FunPtr ptr ;
@@ -81,11 +82,11 @@ class D2 : public Rcpp::VectorBase< REALSXP, NA, D2<RTYPE,NA,T> > {
     D2( FunPtr ptr_, const VEC_TYPE& vec_, double p0_, double p1_ , bool log_) :
         ptr(ptr_), vec(vec_), p0(p0_), p1(p1_), log(log_) {}
 
-    inline double operator[]( int i) const {
+    inline double operator[]( R_xlen_t i) const {
         return ptr( vec[i], p0, p1, log );
     }
 
-    inline int size() const { return vec.size(); }
+    inline R_xlen_t size() const { return vec.size(); }
 
 private:
     FunPtr ptr ;
@@ -103,11 +104,11 @@ class D3 : public Rcpp::VectorBase< REALSXP, NA, D3<RTYPE,NA,T> > {
     D3( FunPtr ptr_, const VEC_TYPE& vec_, double p0_, double p1_, double p2_ , bool log_ ) :
         ptr(ptr_), vec(vec_), p0(p0_), p1(p1_), p2(p2_), log(log_) {}
 
-    inline double operator[]( int i) const {
+    inline double operator[]( R_xlen_t i) const {
         return ptr( vec[i], p0, p1, p2, log );
     }
 
-    inline int size() const { return vec.size(); }
+    inline R_xlen_t size() const { return vec.size(); }
 
 private:
     FunPtr ptr ;
@@ -129,11 +130,11 @@ class P0 : public Rcpp::VectorBase< REALSXP, NA, P0<RTYPE,NA,T> >{
         bool lower_tail = true, bool log_ = false ) :
         ptr(ptr_), vec(vec_), lower(lower_tail), log(log_) {}
 
-    inline double operator[]( int i) const {
+    inline double operator[]( R_xlen_t i) const {
         return ptr( vec[i], lower, log );
     }
 
-    inline int size() const { return vec.size(); }
+    inline R_xlen_t size() const { return vec.size(); }
 
 private:
     FunPtr ptr ;
@@ -153,11 +154,11 @@ class P1 : public Rcpp::VectorBase< REALSXP, NA, P1<RTYPE,NA,T> >{
         bool lower_tail = true, bool log_ = false ) :
         ptr(ptr_), vec(vec_), p0(p0_), lower(lower_tail), log(log_) {}
 
-    inline double operator[]( int i) const {
+    inline double operator[]( R_xlen_t i) const {
         return ptr( vec[i], p0, lower, log );
     }
 
-    inline int size() const { return vec.size(); }
+    inline R_xlen_t size() const { return vec.size(); }
 
 private:
     FunPtr ptr ;
@@ -178,11 +179,11 @@ class P2 : public Rcpp::VectorBase< REALSXP, NA, P2<RTYPE,NA,T> >{
         bool lower_tail = true, bool log_ = false ) :
         ptr(ptr_), vec(vec_), p0(p0_), p1(p1_), lower(lower_tail), log(log_) {}
 
-    inline double operator[]( int i) const {
+    inline double operator[]( R_xlen_t i) const {
         return ptr( vec[i], p0, p1, lower, log );
     }
 
-    inline int size() const { return vec.size(); }
+    inline R_xlen_t size() const { return vec.size(); }
 
 private:
     FunPtr ptr ;
@@ -201,11 +202,11 @@ class P3 : public Rcpp::VectorBase< REALSXP, NA, P3<RTYPE,NA,T> >{
         bool lower_tail = true, bool log_ = false ) :
         ptr(ptr_), vec(vec_), p0(p0_), p1(p1_), p2(p2_), lower(lower_tail), log(log_) {}
 
-    inline double operator[]( int i) const {
+    inline double operator[]( R_xlen_t i) const {
         return ptr( vec[i], p0, p1, p2, lower, log );
     }
 
-    inline int size() const { return vec.size(); }
+    inline R_xlen_t size() const { return vec.size(); }
 
 private:
     FunPtr ptr ;
@@ -227,11 +228,11 @@ class Q0 : public Rcpp::VectorBase< REALSXP, NA, Q0<RTYPE,NA,T> >{
         bool lower_tail = true, bool log_ = false ) :
         ptr(ptr_), vec(vec_), lower(lower_tail), log(log_) {}
 
-    inline double operator[]( int i) const {
+    inline double operator[]( R_xlen_t i) const {
         return ptr( vec[i], lower, log );
     }
 
-    inline int size() const { return vec.size(); }
+    inline R_xlen_t size() const { return vec.size(); }
 
 private:
     FunPtr ptr ;
@@ -250,11 +251,11 @@ class Q1 : public Rcpp::VectorBase< REALSXP, NA, Q1<RTYPE,NA,T> >{
         bool lower_tail = true, bool log_ = false ) :
         ptr(ptr_), vec(vec_), p0(p0_), lower(lower_tail), log(log_) {}
 
-    inline double operator[]( int i) const {
+    inline double operator[]( R_xlen_t i) const {
         return ptr( vec[i], p0, lower, log );
     }
 
-    inline int size() const { return vec.size(); }
+    inline R_xlen_t size() const { return vec.size(); }
 
 private:
     FunPtr ptr ;
@@ -274,11 +275,11 @@ class Q2 : public Rcpp::VectorBase< REALSXP, NA, Q2<RTYPE,NA,T> >{
         bool lower_tail = true, bool log_ = false ) :
         ptr(ptr_), vec(vec_), p0(p0_), p1(p1_), lower(lower_tail), log(log_) {}
 
-    inline double operator[]( int i) const {
+    inline double operator[]( R_xlen_t i) const {
         return ptr( vec[i], p0, p1, lower, log );
     }
 
-    inline int size() const { return vec.size(); }
+    inline R_xlen_t size() const { return vec.size(); }
 
 private:
     FunPtr ptr ;
@@ -298,11 +299,11 @@ class Q3 : public Rcpp::VectorBase< REALSXP, NA, Q3<RTYPE,NA,T> >{
         bool lower_tail = true, bool log_ = false ) :
         ptr(ptr_), vec(vec_), p0(p0_), p1(p1_), p2(p2_), lower(lower_tail), log(log_) {}
 
-    inline double operator[]( int i) const {
+    inline double operator[]( R_xlen_t i) const {
         return ptr( vec[i], p0, p1, p2, lower, log );
     }
 
-    inline int size() const { return vec.size(); }
+    inline R_xlen_t size() const { return vec.size(); }
 
 private:
     FunPtr ptr ;
diff --git a/inst/include/Rcpp/sugar/Range.h b/inst/include/Rcpp/sugar/Range.h
index e38bd6983..08da6d1c4 100644
--- a/inst/include/Rcpp/sugar/Range.h
+++ b/inst/include/Rcpp/sugar/Range.h
@@ -2,7 +2,8 @@
 //
 // Range.h: Rcpp R/C++ interface class library --
 //
-// Copyright (C) 2010 - 2013 Dirk Eddelbuettel and Romain Francois
+// Copyright (C) 2010 - 2025 Dirk Eddelbuettel and Romain Francois
+// Copyright (C) 2026        Dirk Eddelbuettel, Romain Francois and Iñaki Ucar
 //
 // This file is part of Rcpp.
 //
@@ -36,8 +37,8 @@ namespace Rcpp{
             return end_ - start + 1;
         }
 
-        inline R_xlen_t operator[]( R_xlen_t i) const {
-            return start + i ;
+        inline int operator[]( R_xlen_t i) const {
+            return static_cast<int>(start + i) ;
         }
 
         Range& operator++() {
diff --git a/inst/include/Rcpp/sugar/functions/head.h b/inst/include/Rcpp/sugar/functions/head.h
index 7bf724016..32fa7a3ec 100644
--- a/inst/include/Rcpp/sugar/functions/head.h
+++ b/inst/include/Rcpp/sugar/functions/head.h
@@ -2,7 +2,8 @@
 //
 // head.h: Rcpp R/C++ interface class library -- head
 //
-// Copyright (C) 2010 - 2011 Dirk Eddelbuettel and Romain Francois
+// Copyright (C) 2010 - 2025 Dirk Eddelbuettel and Romain Francois
+// Copyright (C) 2026        Dirk Eddelbuettel, Romain Francois and Iñaki Ucar
 //
 // This file is part of Rcpp.
 //
@@ -44,7 +45,7 @@ class Head : public Rcpp::VectorBase< RTYPE ,NA, Head<RTYPE,NA,T> > {
 
 private:
 	const VEC_TYPE& object ;
-	int n ;
+	R_xlen_t n ;
 } ;
 
 } // sugar
diff --git a/inst/include/Rcpp/sugar/functions/rowSums.h b/inst/include/Rcpp/sugar/functions/rowSums.h
index ec9b26acb..2afcd954b 100644
--- a/inst/include/Rcpp/sugar/functions/rowSums.h
+++ b/inst/include/Rcpp/sugar/functions/rowSums.h
@@ -120,7 +120,7 @@ class RowSumsImpl :
     {}
 
     return_vector get() const {
-        R_xlen_t i, j, nr = ref.nrow(), nc = ref.ncol();
+        int i, j, nr = static_cast<int>(ref.nrow()), nc = static_cast<int>(ref.ncol());
         return_vector res(nr);
 
         for (j = 0; j < nc; j++) {
@@ -164,7 +164,7 @@ public:
     {}                                                                                                      \
                                                                                                             \
     return_vector get() const {                                                                             \
-        R_xlen_t i, j, nr = ref.nrow(), nc = ref.ncol();                                                    \
+        int i, j, nr = static_cast<int>(ref.nrow()), nc = static_cast<int>(ref.ncol());                     \
         return_vector res(nr);                                                                              \
                                                                                                             \
         for (j = 0; j < nc; j++) {                                                                          \
@@ -207,7 +207,7 @@ class RowSumsImpl<RTYPE, NA, T, true> :
     {}
 
     return_vector get() const {
-        R_xlen_t i, j, nr = ref.nrow(), nc = ref.ncol();
+        int i, j, nr = static_cast<int>(ref.nrow()), nc = static_cast<int>(ref.ncol());
         return_vector res(nr);
 
         stored_type current = stored_type();
@@ -248,7 +248,7 @@ public:
     {}                                                                                                      \
                                                                                                             \
     return_vector get() const {                                                                             \
-        R_xlen_t i, j, nr = ref.nrow(), nc = ref.ncol();                                                    \
+        int i, j, nr = static_cast<int>(ref.nrow()), nc = static_cast<int>(ref.ncol());                     \
         return_vector res(nr);                                                                              \
                                                                                                             \
         stored_type current = stored_type();                                                                \
@@ -301,7 +301,7 @@ class ColSumsImpl :
     {}
 
     return_vector get() const {
-        R_xlen_t i, j, nr = ref.nrow(), nc = ref.ncol();
+        int i, j, nr = static_cast<int>(ref.nrow()), nc = static_cast<int>(ref.ncol());
         return_vector res(nc);
 
         for (j = 0; j < nc; j++) {
@@ -337,7 +337,7 @@ public:
     {}                                                                                                      \
                                                                                                             \
     return_vector get() const {                                                                             \
-        R_xlen_t i, j, nr = ref.nrow(), nc = ref.ncol();                                                    \
+        int i, j, nr = static_cast<int>(ref.nrow()), nc = static_cast<int>(ref.ncol());                     \
         return_vector res(nc);                                                                              \
                                                                                                             \
         for (j = 0; j < nc; j++) {                                                                          \
@@ -380,7 +380,7 @@ class ColSumsImpl<RTYPE, NA, T, true> :
     {}
 
     return_vector get() const {
-        R_xlen_t i, j, nr = ref.nrow(), nc = ref.ncol();
+        int i, j, nr = static_cast<int>(ref.nrow()), nc = static_cast<int>(ref.ncol());
         return_vector res(nc);
 
         stored_type current = stored_type();
@@ -421,7 +421,7 @@ public:
     {}                                                                                                      \
                                                                                                             \
     return_vector get() const {                                                                             \
-        R_xlen_t i, j, nr = ref.nrow(), nc = ref.ncol();                                                    \
+        int i, j, nr = static_cast<int>(ref.nrow()), nc = static_cast<int>(ref.ncol());                     \
         return_vector res(nc);                                                                              \
                                                                                                             \
         stored_type current = stored_type();                                                                \
@@ -477,7 +477,7 @@ class RowMeansImpl :
     {}
 
     return_vector get() const {
-        R_xlen_t i, j, nr = ref.nrow(), nc = ref.ncol();
+        int i, j, nr = static_cast<int>(ref.nrow()), nc = static_cast<int>(ref.ncol());
         return_vector res(nr);
 
         for (j = 0; j < nc; j++) {
@@ -517,7 +517,7 @@ public:
     {}                                                                                                          \
                                                                                                                 \
     return_vector get() const {                                                                                 \
-        R_xlen_t i, j, nr = ref.nrow(), nc = ref.ncol();                                                        \
+        int i, j, nr = static_cast<int>(ref.nrow()), nc = static_cast<int>(ref.ncol());                         \
         return_vector res(nr);                                                                                  \
                                                                                                                 \
         for (j = 0; j < nc; j++) {                                                                              \
@@ -564,7 +564,7 @@ class RowMeansImpl<RTYPE, NA, T, true> :
     {}
 
     return_vector get() const {
-        R_xlen_t i, j, nr = ref.nrow(), nc = ref.ncol();
+        int i, j, nr = static_cast<int>(ref.nrow()), nc = static_cast<int>(ref.ncol());
         return_vector res(nr);
 
         std::vector<R_xlen_t> n_ok(nr, 0);
@@ -616,7 +616,7 @@ public:
     {}                                                                                                          \
                                                                                                                 \
     return_vector get() const {                                                                                 \
-        R_xlen_t i, j, nr = ref.nrow(), nc = ref.ncol();                                                        \
+        int i, j, nr = static_cast<int>(ref.nrow()), nc = static_cast<int>(ref.ncol());                         \
         return_vector res(nr);                                                                                  \
                                                                                                                 \
         std::vector<R_xlen_t> n_ok(nr, 0);                                                                      \
@@ -677,7 +677,7 @@ class ColMeansImpl :
     {}
 
     return_vector get() const {
-        R_xlen_t i, j, nr = ref.nrow(), nc = ref.ncol();
+        int i, j, nr = static_cast<int>(ref.nrow()), nc = static_cast<int>(ref.ncol());
         return_vector res(nc);
 
         for (j = 0; j < nc; j++) {
@@ -717,7 +717,7 @@ public:
     {}                                                                                                          \
                                                                                                                 \
     return_vector get() const {                                                                                 \
-        R_xlen_t i, j, nr = ref.nrow(), nc = ref.ncol();                                                        \
+        int i, j, nr = static_cast<int>(ref.nrow()), nc = static_cast<int>(ref.ncol());                         \
         return_vector res(nc);                                                                                  \
                                                                                                                 \
         for (j = 0; j < nc; j++) {                                                                              \
@@ -764,7 +764,7 @@ class ColMeansImpl<RTYPE, NA, T, true> :
     {}
 
     return_vector get() const {
-        R_xlen_t i, j, nr = ref.nrow(), nc = ref.ncol();
+        int i, j, nr = static_cast<int>(ref.nrow()), nc = static_cast<int>(ref.ncol());
         return_vector res(nc);
 
         std::vector<R_xlen_t> n_ok(nc, 0);
@@ -816,7 +816,7 @@ public:
     {}                                                                                                          \
                                                                                                                 \
     return_vector get() const {                                                                                 \
-        R_xlen_t i, j, nr = ref.nrow(), nc = ref.ncol();                                                        \
+        int i, j, nr = static_cast<int>(ref.nrow()), nc = static_cast<int>(ref.ncol());                         \
         return_vector res(nc);                                                                                  \
                                                                                                                 \
         std::vector<R_xlen_t> n_ok(nc, 0);                                                                      \
diff --git a/inst/include/Rcpp/sugar/functions/sample.h b/inst/include/Rcpp/sugar/functions/sample.h
index 50bd63813..baf0a9eb3 100644
--- a/inst/include/Rcpp/sugar/functions/sample.h
+++ b/inst/include/Rcpp/sugar/functions/sample.h
@@ -2,7 +2,8 @@
 //
 // sample.h: Rcpp R/C++ interface class library -- sample
 //
-// Copyright (C) 2016 Nathan Russell
+// Copyright (C) 2016 - 2025 Nathan Russell
+// Copyright (C) 2026        Nathan Russell and Iñaki Ucar
 //
 // This file is part of Rcpp.
 //
@@ -113,7 +114,7 @@ inline Vector<INTSXP> SampleReplace(Vector<REALSXP>& p, int n, int k, bool one_b
 template <int RTYPE>
 inline Vector<RTYPE> SampleReplace(Vector<REALSXP>& p, int k, const Vector<RTYPE>& ref)
 {
-    int n = ref.size();
+    int n = static_cast<int>(ref.size());
 
     Vector<INTSXP> perm = no_init(n);
     Vector<RTYPE> ans = no_init(k);
@@ -200,7 +201,7 @@ inline Vector<INTSXP> WalkerSample(const Vector<REALSXP>& p, int n, int nans, bo
 template <int RTYPE>
 inline Vector<RTYPE> WalkerSample(const Vector<REALSXP>& p, int nans, const Vector<RTYPE>& ref)
 {
-    int n = ref.size();
+    int n = static_cast<int>(ref.size());
 
     Vector<INTSXP> a = no_init(n);
     Vector<RTYPE> ans = no_init(nans);
@@ -294,7 +295,7 @@ inline Vector<INTSXP> SampleNoReplace(Vector<REALSXP>& p, int n, int nans, bool
 template <int RTYPE>
 inline Vector<RTYPE> SampleNoReplace(Vector<REALSXP>& p, int nans, const Vector<RTYPE>& ref)
 {
-    int n = ref.size();
+    int n = static_cast<int>(ref.size());
 
     Vector<INTSXP> perm = no_init(n);
     Vector<RTYPE> ans = no_init(nans);
@@ -366,7 +367,7 @@ inline Vector<INTSXP> EmpiricalSample(int n, int size, bool replace, bool one_ba
 template <int RTYPE>
 inline Vector<RTYPE> EmpiricalSample(int size, bool replace, const Vector<RTYPE>& ref)
 {
-    int n = ref.size();
+    int n = static_cast<int>(ref.size());
 
     Vector<RTYPE> ans = no_init(size);
     typename Vector<RTYPE>::iterator ians = ans.begin(), eans = ans.end();
@@ -436,7 +437,7 @@ template <int RTYPE>
 inline Vector<RTYPE>
 sample(const Vector<RTYPE>& x, int size, bool replace = false, sugar::probs_t probs = R_NilValue)
 {
-    int n = x.size();
+    int n = static_cast<int>(x.size());
 
     if (probs.isNotNull()) {
         Vector<REALSXP> p = clone(probs.get());
diff --git a/inst/include/Rcpp/sugar/functions/seq_along.h b/inst/include/Rcpp/sugar/functions/seq_along.h
index fdc2108d6..247e9af2c 100644
--- a/inst/include/Rcpp/sugar/functions/seq_along.h
+++ b/inst/include/Rcpp/sugar/functions/seq_along.h
@@ -2,7 +2,8 @@
 //
 // seq_along.h: Rcpp R/C++ interface class library -- any
 //
-// Copyright (C) 2010 - 2011 Dirk Eddelbuettel and Romain Francois
+// Copyright (C) 2010 - 2025 Dirk Eddelbuettel and Romain Francois
+// Copyright (C) 2026        Dirk Eddelbuettel, Romain Francois and Iñaki Ucar
 //
 // This file is part of Rcpp.
 //
@@ -29,8 +30,8 @@ class SeqLen : public VectorBase< INTSXP,false,SeqLen > {
 public:
         SeqLen( R_xlen_t len_ ) : len(len_){}
 
-        inline R_xlen_t operator[]( R_xlen_t i ) const {
-		return 1 + i ;
+        inline int operator[]( R_xlen_t i ) const {
+		return static_cast<int>(1 + i) ;
 	}
         inline R_xlen_t size() const { return len ; }
 
diff --git a/inst/include/Rcpp/sugar/functions/var.h b/inst/include/Rcpp/sugar/functions/var.h
index 419d0cbb8..6e064c66a 100644
--- a/inst/include/Rcpp/sugar/functions/var.h
+++ b/inst/include/Rcpp/sugar/functions/var.h
@@ -2,8 +2,9 @@
 //
 // var.h: Rcpp R/C++ interface class library -- var
 //
-// Copyright (C) 2011 Dirk Eddelbuettel and Romain Francois
-// Copyright (C) 2015 Wush Wu
+// Copyright (C) 2011 - 2014 Dirk Eddelbuettel and Romain Francois
+// Copyright (C) 2015 - 2025 Dirk Eddelbuettel, Romain Francois and Wush Wu
+// Copyright (C) 2026        Dirk Eddelbuettel, Romain Francois, Wush Wu and Iñaki Ucar
 //
 // This file is part of Rcpp.
 //
@@ -39,7 +40,7 @@ class Var : public Lazy< double , Var<RTYPE,NA,T> > {
         double sum_squared_deviations = 0.0;
         for (R_xlen_t i = 0; i != sample_size; ++i)
             sum_squared_deviations += std::pow(object[i] - average, 2.0);
-        return sum_squared_deviations / (sample_size - 1);
+        return sum_squared_deviations / static_cast<double>(sample_size - 1);
     }
 
 private:
@@ -61,7 +62,7 @@ class Var<CPLXSXP,NA,T> : public Lazy< double , Var<CPLXSXP,NA,T> > {
             const Rcomplex deviation = object[i] - average;
             sum_squared_deviations_magnitudes += deviation.r * deviation.r + deviation.i * deviation.i;
         }
-        return sum_squared_deviations_magnitudes / (sample_size - 1);
+        return sum_squared_deviations_magnitudes / static_cast<double>(sample_size - 1);
     }
 
 private:
diff --git a/inst/include/Rcpp/sugar/matrix/col.h b/inst/include/Rcpp/sugar/matrix/col.h
index dea30b622..6575720e5 100644
--- a/inst/include/Rcpp/sugar/matrix/col.h
+++ b/inst/include/Rcpp/sugar/matrix/col.h
@@ -35,7 +35,7 @@ class Col : public MatrixBase<
 public:
 	typedef Rcpp::MatrixBase<RTYPE,LHS_NA,LHS_T> LHS_TYPE ;
 
-	Col( const LHS_TYPE& lhs) : nr( lhs.ncol() ), nc( lhs.ncol() ) {}
+	Col( const LHS_TYPE& lhs) : nr( static_cast<int>(lhs.ncol()) ), nc( static_cast<int>(lhs.ncol()) ) {}
 
 	inline int operator()( int /*i*/, int j ) const {
 		return j + 1 ;
diff --git a/inst/include/Rcpp/sugar/matrix/diag.h b/inst/include/Rcpp/sugar/matrix/diag.h
index eaae59851..af2941645 100644
--- a/inst/include/Rcpp/sugar/matrix/diag.h
+++ b/inst/include/Rcpp/sugar/matrix/diag.h
@@ -2,7 +2,8 @@
 //
 // diag.h: Rcpp R/C++ interface class library -- diag
 //
-// Copyright (C) 2010 - 2011 Dirk Eddelbuettel and Romain Francois
+// Copyright (C) 2010 - 2025 Dirk Eddelbuettel and Romain Francois
+// Copyright (C) 2026        Dirk Eddelbuettel, Romain Francois and Iñaki Ucar
 //
 // This file is part of Rcpp.
 //
@@ -32,13 +33,13 @@ class Diag_Extractor : public Rcpp::VectorBase< RTYPE ,NA, Diag_Extractor<RTYPE,
 	typedef typename Rcpp::traits::storage_type<RTYPE>::type STORAGE ;
 
 	Diag_Extractor( const MAT_TYPE& object_ ) : object(object_), n(0) {
-		int nr = object.nrow() ;
-		int nc = object.ncol() ;
+		int nr = static_cast<int>(object.nrow()) ;
+		int nc = static_cast<int>(object.ncol()) ;
 		n = (nc < nr ) ? nc : nr ;
 	}
 
-	inline STORAGE operator[]( int i ) const {
-		return object( i, i ) ;
+	inline STORAGE operator[]( R_xlen_t i ) const {
+		return object( static_cast<int>(i), static_cast<int>(i) ) ;
 	}
 	inline R_xlen_t size() const { return n; }
 
@@ -54,7 +55,7 @@ class Diag_Maker : public Rcpp::MatrixBase< RTYPE ,NA, Diag_Maker<RTYPE,NA,T> >
 	typedef typename Rcpp::VectorBase<RTYPE,NA,T> VEC_TYPE ;
 	typedef typename Rcpp::traits::storage_type<RTYPE>::type STORAGE ;
 
-	Diag_Maker( const VEC_TYPE& object_ ) : object(object_), n(object_.size()) {}
+	Diag_Maker( const VEC_TYPE& object_ ) : object(object_), n(static_cast<int>(object_.size())) {}
 
 	inline STORAGE operator()( int i, int j ) const {
 		return (i==j) ? object[i] : 0 ;
diff --git a/inst/include/Rcpp/sugar/matrix/lower_tri.h b/inst/include/Rcpp/sugar/matrix/lower_tri.h
index 99f501ad9..af3bf86f2 100644
--- a/inst/include/Rcpp/sugar/matrix/lower_tri.h
+++ b/inst/include/Rcpp/sugar/matrix/lower_tri.h
@@ -3,7 +3,8 @@
 // lower_tri.h: Rcpp R/C++ interface class library -- lower.tri
 //
 // Copyright (C) 2010 - 2017 Dirk Eddelbuettel and Romain Francois
-// Copyright (C) 2017    Dirk Eddelbuettel, Romain Francois, and Nathan Russell
+// Copyright (C) 2017 - 2025 Dirk Eddelbuettel, Romain Francois, and Nathan Russell
+// Copyright (C) 2026        Dirk Eddelbuettel, Romain Francois, Nathan Russell and Iñaki Ucar
 //
 // This file is part of Rcpp.
 //
@@ -32,8 +33,8 @@ class LowerTri : public MatrixBase<LGLSXP, false, LowerTri<RTYPE, NA, T> > {
     typedef Rcpp::MatrixBase<RTYPE, NA, T> MatBase;
 
     LowerTri(const T& lhs, bool diag)
-        : nr(lhs.nrow()),
-          nc(lhs.ncol()),
+        : nr(static_cast<int>(lhs.nrow())),
+          nc(static_cast<int>(lhs.ncol())),
           getter(diag ? (&LowerTri::get_diag_true) : (&LowerTri::get_diag_false))
     {}
 
diff --git a/inst/include/Rcpp/sugar/matrix/outer.h b/inst/include/Rcpp/sugar/matrix/outer.h
index 5a7b4aa03..8a52bcb5c 100644
--- a/inst/include/Rcpp/sugar/matrix/outer.h
+++ b/inst/include/Rcpp/sugar/matrix/outer.h
@@ -52,7 +52,7 @@ class Outer : public MatrixBase<
     typedef typename Rcpp::traits::storage_type<RESULT_R_TYPE>::type STORAGE ;
 
     Outer( const LHS_TYPE& lhs_, const RHS_TYPE& rhs_, Function fun_ ) :
-        lhs(lhs_), rhs(rhs_), fun(fun_), nr(lhs_.size()), nc(rhs_.size()) {}
+        lhs(lhs_), rhs(rhs_), fun(fun_), nr(static_cast<int>(lhs_.size())), nc(static_cast<int>(rhs_.size())) {}
 
     inline STORAGE operator()( int i, int j ) const {
         return converter_type::get( fun( lhs[i], rhs[j] ) );
diff --git a/inst/include/Rcpp/sugar/matrix/row.h b/inst/include/Rcpp/sugar/matrix/row.h
index 30b644236..4b8de59e9 100644
--- a/inst/include/Rcpp/sugar/matrix/row.h
+++ b/inst/include/Rcpp/sugar/matrix/row.h
@@ -35,7 +35,7 @@ class Row : public MatrixBase<
 public:
 	typedef Rcpp::MatrixBase<RTYPE,LHS_NA,LHS_T> LHS_TYPE ;
 
-	Row( const LHS_TYPE& lhs) : nr( lhs.nrow() ), nc( lhs.ncol() ) {}
+	Row( const LHS_TYPE& lhs) : nr( static_cast<int>(lhs.nrow()) ), nc( static_cast<int>(lhs.ncol()) ) {}
 
 	inline int operator()( int i, int /*j*/ ) const {
 		return i + 1 ;
diff --git a/inst/include/Rcpp/sugar/matrix/upper_tri.h b/inst/include/Rcpp/sugar/matrix/upper_tri.h
index b6f1b85f2..60c290b15 100644
--- a/inst/include/Rcpp/sugar/matrix/upper_tri.h
+++ b/inst/include/Rcpp/sugar/matrix/upper_tri.h
@@ -3,7 +3,8 @@
 // upper_tri.h: Rcpp R/C++ interface class library -- upper.tri
 //
 // Copyright (C) 2010 - 2017 Dirk Eddelbuettel and Romain Francois
-// Copyright (C) 2017        Dirk Eddelbuettel, Romain Francois, and Nathan Russell
+// Copyright (C) 2017 - 2025 Dirk Eddelbuettel, Romain Francois, and Nathan Russell
+// Copyright (C) 2026        Dirk Eddelbuettel, Romain Francois, Nathan Russell and Iñaki Ucar
 //
 // This file is part of Rcpp.
 //
@@ -32,8 +33,8 @@ class UpperTri : public MatrixBase<LGLSXP, false, UpperTri<RTYPE, NA, T> > {
     typedef Rcpp::MatrixBase<RTYPE, NA, T> MatBase;
 
     UpperTri(const T& lhs, bool diag)
-        : nr(lhs.nrow()),
-          nc(lhs.ncol()),
+        : nr(static_cast<int>(lhs.nrow())),
+          nc(static_cast<int>(lhs.ncol())),
           getter(diag ? (&UpperTri::get_diag_true) : (&UpperTri::get_diag_false))
     {}
 
diff --git a/inst/include/Rcpp/sugar/operators/Comparator_With_One_Value.h b/inst/include/Rcpp/sugar/operators/Comparator_With_One_Value.h
index 9452a259c..7286fdeda 100644
--- a/inst/include/Rcpp/sugar/operators/Comparator_With_One_Value.h
+++ b/inst/include/Rcpp/sugar/operators/Comparator_With_One_Value.h
@@ -31,7 +31,7 @@ class Comparator_With_One_Value : public ::Rcpp::VectorBase< LGLSXP, true, Compa
 public:
 	typedef typename Rcpp::VectorBase<RTYPE,NA,T> VEC_TYPE ;
 	typedef typename traits::storage_type<RTYPE>::type STORAGE ;
-	typedef int (Comparator_With_One_Value::*METHOD)(int) const ;
+	typedef int (Comparator_With_One_Value::*METHOD)(R_xlen_t) const ;
 
 	Comparator_With_One_Value( const VEC_TYPE& lhs_, STORAGE rhs_ ) :
 		lhs(lhs_), rhs(rhs_), m(), op() {
@@ -54,8 +54,8 @@ class Comparator_With_One_Value : public ::Rcpp::VectorBase< LGLSXP, true, Compa
 	METHOD m ;
 	Operator op ;
 
-	inline int rhs_is_na(int /*i*/) const { return rhs ; }
-	inline int rhs_is_not_na(int i) const {
+	inline int rhs_is_na(R_xlen_t /*i*/) const { return NA_INTEGER ; }
+	inline int rhs_is_not_na(R_xlen_t i) const {
 		STORAGE x = lhs[i] ;
 		return Rcpp::traits::is_na<RTYPE>(x) ? NA_INTEGER : op( x, rhs ) ;
 	}
@@ -70,7 +70,7 @@ class Comparator_With_One_Value<RTYPE,Operator,false,T> :
 public:
 	typedef typename Rcpp::VectorBase<RTYPE,false,T> VEC_TYPE ;
 	typedef typename traits::storage_type<RTYPE>::type STORAGE ;
-	typedef int (Comparator_With_One_Value::*METHOD)(int) const ;
+	typedef int (Comparator_With_One_Value::*METHOD)(R_xlen_t) const ;
 
 	Comparator_With_One_Value( const VEC_TYPE& lhs_, STORAGE rhs_ ) :
 		lhs(lhs_), rhs(rhs_), m(), op() {
@@ -93,8 +93,8 @@ class Comparator_With_One_Value<RTYPE,Operator,false,T> :
 	METHOD m ;
 	Operator op ;
 
-	inline int rhs_is_na(int /*i*/) const { return rhs ; }
-	inline int rhs_is_not_na(int i) const {
+	inline int rhs_is_na(R_xlen_t /*i*/) const { return NA_INTEGER ; }
+	inline int rhs_is_not_na(R_xlen_t i) const {
 		return op( lhs[i], rhs ) ;
 	}
 
diff --git a/inst/include/Rcpp/vector/ListOf.h b/inst/include/Rcpp/vector/ListOf.h
index 46aed35c8..6f0290274 100644
--- a/inst/include/Rcpp/vector/ListOf.h
+++ b/inst/include/Rcpp/vector/ListOf.h
@@ -40,10 +40,9 @@ class ListOf
         std::transform(list.begin(), list.end(), list.begin(), as<T>);
     }
 
-    template <typename U>
-    ListOf(const U& data_): list(data_) {
-        std::transform(list.begin(), list.end(), list.begin(), as<T>);
-    }
+    template <typename U,
+              typename std::enable_if<std::is_convertible<U, SEXP>::value, int>::type = 0>
+    ListOf(const U& data_): ListOf(static_cast<SEXP>(data_)) {}
 
     ListOf(const ListOf& other): list(other.list) {}
 
diff --git a/inst/include/Rcpp/vector/Matrix.h b/inst/include/Rcpp/vector/Matrix.h
index c34843a58..137de2500 100644
--- a/inst/include/Rcpp/vector/Matrix.h
+++ b/inst/include/Rcpp/vector/Matrix.h
@@ -2,7 +2,8 @@
 //
 // Matrix.h: Rcpp R/C++ interface class library -- matrices
 //
-// Copyright (C) 2010 - 2016  Dirk Eddelbuettel and Romain Francois
+// Copyright (C) 2010 - 2025 Dirk Eddelbuettel and Romain Francois
+// Copyright (C) 2026        Dirk Eddelbuettel, Romain Francois and Iñaki Ucar
 //
 // This file is part of Rcpp.
 //
@@ -74,7 +75,7 @@ class Matrix : public Vector<RTYPE, StoragePolicy>, public MatrixBase<RTYPE, tru
     Matrix( const Matrix& other) : VECTOR( other.get__() ), nrows(other.nrows) {}
 
     template <bool NA, typename MAT>
-    Matrix( const MatrixBase<RTYPE,NA,MAT>& other ) : VECTOR( Rf_allocMatrix( RTYPE, other.nrow(), other.ncol() ) ), nrows(other.nrow()) {
+    Matrix( const MatrixBase<RTYPE,NA,MAT>& other ) : VECTOR( Rf_allocMatrix( RTYPE, static_cast<int>(other.nrow()), static_cast<int>(other.ncol()) ) ), nrows(static_cast<int>(other.nrow())) {
         import_matrix_expression<NA,MAT>( other, nrows, ncol() ) ;
     }
 
@@ -135,10 +136,10 @@ class Matrix : public Vector<RTYPE, StoragePolicy>, public MatrixBase<RTYPE, tru
     }
 
     inline Proxy operator()( const size_t& i, const size_t& j) {
-      return static_cast< Vector<RTYPE>* >( this )->operator[]( offset( i, j ) ) ;
+      return static_cast< Vector<RTYPE>* >( this )->operator[]( offset( static_cast<int>(i), static_cast<int>(j) ) ) ;
     }
     inline const_Proxy operator()( const size_t& i, const size_t& j) const {
-       return static_cast< const Vector<RTYPE>* >( this )->operator[]( offset( i, j ) ) ;
+       return static_cast< const Vector<RTYPE>* >( this )->operator[]( offset( static_cast<int>(i), static_cast<int>(j) ) ) ;
     }
 
     inline Proxy at( const size_t& i, const size_t& j) {
diff --git a/inst/include/Rcpp/vector/MatrixBase.h b/inst/include/Rcpp/vector/MatrixBase.h
index 96decae33..13ce8dfce 100644
--- a/inst/include/Rcpp/vector/MatrixBase.h
+++ b/inst/include/Rcpp/vector/MatrixBase.h
@@ -183,7 +183,7 @@ namespace Rcpp{
             }
 
             inline R_xlen_t index() const {
-                return i + nr * j ;
+                return i + static_cast<R_xlen_t>(nr) * j ;
             }
 
         } ;
diff --git a/inst/include/Rcpp/vector/MatrixColumn.h b/inst/include/Rcpp/vector/MatrixColumn.h
index 4154b61be..ffd81721c 100644
--- a/inst/include/Rcpp/vector/MatrixColumn.h
+++ b/inst/include/Rcpp/vector/MatrixColumn.h
@@ -2,7 +2,8 @@
 //
 // MatrixColumn.h: Rcpp R/C++ interface class library -- matrices column
 //
-// Copyright (C) 2010 - 2013 Dirk Eddelbuettel and Romain Francois
+// Copyright (C) 2010 - 2025 Dirk Eddelbuettel and Romain Francois
+// Copyright (C) 2026        Dirk Eddelbuettel, Romain Francois and Iñaki Ucar
 //
 // This file is part of Rcpp.
 //
@@ -76,11 +77,11 @@ class MatrixColumn : public VectorBase<RTYPE,true,MatrixColumn<RTYPE> > {
         return *this ;
     }
 
-    inline Proxy operator[]( int i ){
+    inline Proxy operator[]( R_xlen_t i ){
         return start[i] ;
     }
 
-    inline const_Proxy operator[]( int i ) const {
+    inline const_Proxy operator[]( R_xlen_t i ) const {
         return const_start[i] ;
     }
 
@@ -142,7 +143,7 @@ class ConstMatrixColumn : public VectorBase<RTYPE,true,ConstMatrixColumn<RTYPE>
         n(other.n),
         const_start(other.const_start) {}
 
-    inline const_Proxy operator[]( int i ) const {
+    inline const_Proxy operator[]( R_xlen_t i ) const {
         return const_start[i] ;
     }
 
diff --git a/inst/include/Rcpp/vector/MatrixRow.h b/inst/include/Rcpp/vector/MatrixRow.h
index 5c1a28b5e..2a5945c16 100644
--- a/inst/include/Rcpp/vector/MatrixRow.h
+++ b/inst/include/Rcpp/vector/MatrixRow.h
@@ -2,7 +2,8 @@
 //
 // MatrixRow.h: Rcpp R/C++ interface class library -- matrices row
 //
-// Copyright (C) 2010 - 2013 Dirk Eddelbuettel and Romain Francois
+// Copyright (C) 2010 - 2025 Dirk Eddelbuettel and Romain Francois
+// Copyright (C) 2026        Dirk Eddelbuettel, Romain Francois and Iñaki Ucar
 //
 // This file is part of Rcpp.
 //
@@ -164,12 +165,12 @@ class MatrixRow : public VectorBase< RTYPE, true, MatrixRow<RTYPE> > {
             return *this ;
     }
 
-    inline reference operator[]( int i ){
+    inline reference operator[]( R_xlen_t i ){
         return start[ get_parent_index(i) ] ;
     }
 
-    inline reference operator[]( int i ) const {
-        return parent[ row + static_cast<R_xlen_t>(i) * parent_nrow ] ;
+    inline reference operator[]( R_xlen_t i ) const {
+        return parent[ row + i * parent_nrow ] ;
     }
 
     inline iterator begin(){
@@ -206,9 +207,9 @@ class MatrixRow : public VectorBase< RTYPE, true, MatrixRow<RTYPE> > {
     int parent_nrow ;
     int row ;
 
-    inline R_xlen_t get_parent_index(int i) const {
-        RCPP_DEBUG_4( "MatrixRow<%d>::get_parent_index(int = %d), parent_nrow = %d >> %d\n", RTYPE, i, parent_nrow, static_cast<R_xlen_t>(i) * parent_nrow )
-        return static_cast<R_xlen_t>(i) * parent_nrow ;
+    inline R_xlen_t get_parent_index(R_xlen_t i) const {
+        RCPP_DEBUG_4( "MatrixRow<%d>::get_parent_index(R_xlen_t = %ld), parent_nrow = %d >> %ld\n", RTYPE, i, parent_nrow, i * parent_nrow )
+        return i * parent_nrow ;
     }
 } ;
 
@@ -309,8 +310,8 @@ class ConstMatrixRow : public VectorBase< RTYPE, true, ConstMatrixRow<RTYPE> > {
         row(other.row)
     {} ;
 
-    inline const_reference operator[]( int i ) const {
-        return parent[ row + static_cast<R_xlen_t>(i) * parent_nrow ] ;
+    inline const_reference operator[]( R_xlen_t i ) const {
+        return parent[ row + i * parent_nrow ] ;
     }
 
     inline const_iterator begin() const {
@@ -331,9 +332,9 @@ class ConstMatrixRow : public VectorBase< RTYPE, true, ConstMatrixRow<RTYPE> > {
     int parent_nrow ;
     int row ;
 
-    inline R_xlen_t get_parent_index(int i) const {
-        RCPP_DEBUG_4( "ConstMatrixRow<%d>::get_parent_index(int = %d), parent_nrow = %d >> %d\n", RTYPE, i, parent_nrow, static_cast<R_xlen_t>(i) * parent_nrow )
-        return static_cast<R_xlen_t>(i) * parent_nrow ;
+    inline R_xlen_t get_parent_index(R_xlen_t i) const {
+        RCPP_DEBUG_4( "ConstMatrixRow<%d>::get_parent_index(R_xlen_t = %ld), parent_nrow = %d >> %ld\n", RTYPE, i, parent_nrow, i * parent_nrow )
+        return i * parent_nrow ;
     }
 } ;
 }
diff --git a/inst/include/Rcpp/vector/RangeIndexer.h b/inst/include/Rcpp/vector/RangeIndexer.h
index dafac7d28..e67600b3e 100644
--- a/inst/include/Rcpp/vector/RangeIndexer.h
+++ b/inst/include/Rcpp/vector/RangeIndexer.h
@@ -26,8 +26,8 @@
 #define UNROLL_LOOP(OP)                              \
     typedef typename ::Rcpp::traits::Extractor<RTYPE,NA,T>::type EXT ; \
     const EXT& input( x.get_ref() ) ;                   \
-    int __trip_count = (size_) >> 2;                 \
-    int i=0 ;                                        \
+    R_xlen_t __trip_count = (size_) >> 2;            \
+    R_xlen_t i=0 ;                                   \
     for ( ; __trip_count > 0 ; --__trip_count) {     \
         start[i] OP input[i] ; i++ ;                 \
         start[i] OP input[i] ; i++ ;                 \
diff --git a/inst/include/Rcpp/vector/SubMatrix.h b/inst/include/Rcpp/vector/SubMatrix.h
index 0bda3ab57..142b6591e 100644
--- a/inst/include/Rcpp/vector/SubMatrix.h
+++ b/inst/include/Rcpp/vector/SubMatrix.h
@@ -1,7 +1,8 @@
 
 // SubMatrix.h: Rcpp R/C++ interface class library -- sub matrices
 //
-// Copyright (C) 2010 - 2013 Dirk Eddelbuettel and Romain Francois
+// Copyright (C) 2010 - 2025 Dirk Eddelbuettel and Romain Francois
+// Copyright (C) 2026        Dirk Eddelbuettel, Romain Francois and Iñaki Ucar
 //
 // This file is part of Rcpp.
 //
@@ -34,33 +35,33 @@ class SubMatrix : public Rcpp::MatrixBase< RTYPE, true, SubMatrix<RTYPE> > {
         m(m_),
         iter( static_cast< Vector<RTYPE>& >(m_).begin() + row_range_.get_start() + col_range_.get_start() * m_.nrow() ),
         m_nr( m.nrow() ),
-        nc( col_range_.size() ),
-        nr( row_range_.size() )
+        nc( static_cast<int>(col_range_.size()) ),
+        nr( static_cast<int>(row_range_.size()) )
     {}
 
-    inline R_xlen_t size() const { return ((R_xlen_t)ncol()) * nrow() ; }
-    inline R_xlen_t ncol() const { return nc ; }
-    inline R_xlen_t nrow() const { return nr ; }
+    inline R_xlen_t size() const { return static_cast<R_xlen_t>(ncol()) * nrow() ; }
+    inline int ncol() const { return nc ; }
+    inline int nrow() const { return nr ; }
 
     inline Proxy operator()(int i, int j) const {
-        return iter[ i + j*m_nr ] ;
+        return iter[ i + static_cast<R_xlen_t>(m_nr)*j ] ;
     }
 
-    inline vec_iterator column_iterator( int j ) const { return iter + j*m_nr ; }
+    inline vec_iterator column_iterator( int j ) const { return iter + static_cast<R_xlen_t>(m_nr)*j ; }
 
 private:
     MATRIX& m ;
     vec_iterator iter ;
-    R_xlen_t m_nr, nc, nr ;
+    int m_nr, nc, nr ;
 } ;
 
 template <int RTYPE, template <class> class StoragePolicy >
-Matrix<RTYPE,StoragePolicy>::Matrix( const SubMatrix<RTYPE>& sub ) : VECTOR( Rf_allocMatrix( RTYPE, (int)sub.nrow(), (int)sub.ncol() )), nrows((int)sub.nrow()) {
-    R_xlen_t nc = sub.ncol() ;
+Matrix<RTYPE,StoragePolicy>::Matrix( const SubMatrix<RTYPE>& sub ) : VECTOR( Rf_allocMatrix( RTYPE, sub.nrow(), sub.ncol() )), nrows(sub.nrow()) {
+    int nc = sub.ncol() ;
     iterator start = VECTOR::begin() ;
 	iterator rhs_it ;
-	for( R_xlen_t j=0; j<nc; j++){
-	    rhs_it = sub.column_iterator((int)j) ;
+	for( int j=0; j<nc; j++){
+	    rhs_it = sub.column_iterator(j) ;
 	    for( int i=0; i<nrows; i++, ++start){
 	        *start = rhs_it[i] ;
 	    }
diff --git a/inst/include/Rcpp/vector/Subsetter.h b/inst/include/Rcpp/vector/Subsetter.h
index 4069eebb0..8f97561a7 100644
--- a/inst/include/Rcpp/vector/Subsetter.h
+++ b/inst/include/Rcpp/vector/Subsetter.h
@@ -58,11 +58,11 @@ class SubsetProxy {
 
         if (n == 1) {
             for (R_xlen_t i=0; i < indices_n; ++i) {
-                lhs[ indices[i] ] = other[0];
+                lhs[ indices[i] ] = static_cast<typename LHS_t::stored_type>(other[0]);
             }
         } else if (n == indices_n) {
             for (R_xlen_t i=0; i < n; ++i) {
-                lhs[ indices[i] ] = other[i];
+                lhs[ indices[i] ] = static_cast<typename LHS_t::stored_type>(other[i]);
             }
         } else {
             stop("index error");
@@ -162,7 +162,7 @@ class SubsetProxy {
         indices.reserve(rhs_n);
         std::vector<R_xlen_t> tmp(rhs.size()); // create temp R_xlen_t type indices from reals
         for(size_t i = 0 ; i < tmp.size() ; ++i) {
-            tmp[i] = rhs[i];
+            tmp[i] = static_cast<R_xlen_t>(rhs[i]);
         }
         check_indices(&tmp[0], rhs_n, lhs_n);
         for (R_xlen_t i=0; i < rhs_n; ++i) {
diff --git a/inst/include/Rcpp/vector/Vector.h b/inst/include/Rcpp/vector/Vector.h
index f9efcd554..bfb78106c 100644
--- a/inst/include/Rcpp/vector/Vector.h
+++ b/inst/include/Rcpp/vector/Vector.h
@@ -1,6 +1,7 @@
 // Vector.h: Rcpp R/C++ interface class library -- vectors
 //
-// Copyright (C) 2010 - 2026  Dirk Eddelbuettel, Romain Francois and Iñaki Ucar
+// Copyright (C) 2010 - 2025  Dirk Eddelbuettel and Romain Francois
+// Copyright (C) 2026         Dirk Eddelbuettel, Romain Francois and Iñaki Ucar
 //
 // This file is part of Rcpp.
 //
@@ -75,7 +76,7 @@ class Vector :
     }
 
     template <typename Proxy>
-    Vector( const GenericProxy<Proxy>& proxy ){
+    explicit Vector( const GenericProxy<Proxy>& proxy ){
         Rcpp::Shield<SEXP> safe(proxy.get());
         Storage::set__( r_cast<RTYPE>(safe) ) ;
     }
@@ -278,7 +279,7 @@ class Vector :
     /**
      * offset based on the dimensions of this vector
      */
-    R_xlen_t offset(const int& i, const int& j) const {
+    R_xlen_t offset(const R_xlen_t& i, const R_xlen_t& j) const {
         if( !::Rf_isMatrix(Storage::get__()) ) throw not_a_matrix() ;
 
         /* we need to extract the dimensions */
@@ -291,7 +292,7 @@ class Vector :
                               "column index=%i; column extent=%i].";
             throw index_out_of_bounds(fmt, i, nrow, j, ncol);
         }
-        return i + static_cast<R_xlen_t>(nrow)*j ;
+        return i + nrow*j ;
     }
 
     /**
@@ -368,10 +369,10 @@ class Vector :
     }																				// #nocov end
 
     inline Proxy operator()( const size_t& i, const size_t& j) {
-        return cache.ref( offset(i,j) ) ;
+        return cache.ref( offset(i, j) ) ;
     }
     inline const_Proxy operator()( const size_t& i, const size_t& j) const {
-        return cache.ref( offset(i,j) ) ;
+        return cache.ref( offset(i, j) ) ;
     }
 
     inline NameProxy operator[]( const std::string& name ){
diff --git a/inst/tinytest/cpp/Matrix.cpp b/inst/tinytest/cpp/Matrix.cpp
index aa9b2a27a..430230803 100644
--- a/inst/tinytest/cpp/Matrix.cpp
+++ b/inst/tinytest/cpp/Matrix.cpp
@@ -2,7 +2,8 @@
 //
 // Matrix.cpp: Rcpp R/C++ interface class library -- Matrix unit tests
 //
-// Copyright (C) 2013 - 2016  Dirk Eddelbuettel, Romain Francois and Kevin Ushey
+// Copyright (C) 2013 - 2025 Dirk Eddelbuettel, Romain Francois and Kevin Ushey
+// Copyright (C) 2026        Dirk Eddelbuettel, Romain Francois, Kevin Ushey and Iñaki Ucar
 //
 // This file is part of Rcpp.
 //
@@ -87,7 +88,7 @@ int integer_matrix_indexing( IntegerMatrix m){
 
 // [[Rcpp::export]]
 IntegerVector integer_matrix_indexing_lhs( IntegerVector m ){
-    for( size_t i=0 ; i<4; i++){
+    for( int i=0 ; i<4; i++){
         m(i,i) = 2 * i ;
     }
     return m ;
diff --git a/inst/tinytest/cpp/Module.cpp b/inst/tinytest/cpp/Module.cpp
index b267c18d3..7f3132820 100644
--- a/inst/tinytest/cpp/Module.cpp
+++ b/inst/tinytest/cpp/Module.cpp
@@ -3,7 +3,8 @@
 //
 // Module.cpp: Rcpp R/C++ interface class library -- module unit tests
 //
-// Copyright (C) 2013 - 2015  Dirk Eddelbuettel and Romain Francois
+// Copyright (C) 2013 - 2025 Dirk Eddelbuettel and Romain Francois
+// Copyright (C) 2026        Dirk Eddelbuettel, Romain Francois and Iñaki Ucar
 //
 // This file is part of Rcpp.
 //
@@ -49,13 +50,13 @@ void bla2(int x, double y) {
 }
 
 int test_reference(std::vector<double>& ref) {
-    return ref.size();
+    return static_cast<int>(ref.size());
 }
 int test_const_reference(const std::vector<double>& ref) {
-    return ref.size();
+    return static_cast<int>(ref.size());
 }
 int test_const(const std::vector<double> ref) {
-    return ref.size();
+    return static_cast<int>(ref.size());
 }
 
 class ModuleWorld {
diff --git a/inst/tinytest/cpp/String.cpp b/inst/tinytest/cpp/String.cpp
index 5d12a2165..37392aadf 100644
--- a/inst/tinytest/cpp/String.cpp
+++ b/inst/tinytest/cpp/String.cpp
@@ -28,14 +28,14 @@ class StringConv{
         nr(old_.size()), old(old_), new_(new__){}
 
     String operator()(String text) const {
-        for( int i=0; i<nr; i++){
+        for( R_xlen_t i=0; i<nr; i++){
             text.replace_all( old[i], new_[i] ) ;
         }
         return text ;
     }
 
 private:
-    int nr ;
+    R_xlen_t nr ;
     CharacterVector old ;
     CharacterVector new_ ;
 } ;
diff --git a/inst/tinytest/cpp/Vector.cpp b/inst/tinytest/cpp/Vector.cpp
index f7703d731..3ca29f39d 100644
--- a/inst/tinytest/cpp/Vector.cpp
+++ b/inst/tinytest/cpp/Vector.cpp
@@ -96,8 +96,8 @@ ComplexVector complex_(){
 
 // [[Rcpp::export]]
 ComplexVector complex_CPLXSXP( ComplexVector x ){
-    int nn = x.size();
-    for( int i=0; i<nn; i++) {
+    R_xlen_t nn = x.size();
+    for( R_xlen_t i=0; i<nn; i++) {
         x[i].r = x[i].r*2 ;
         x[i].i = x[i].i*2 ;
     }
@@ -107,7 +107,7 @@ ComplexVector complex_CPLXSXP( ComplexVector x ){
 // [[Rcpp::export]]
 ComplexVector complex_INTSXP( SEXP vec ){
     ComplexVector x(vec);
-    int nn = x.size();
+    R_xlen_t nn = x.size();
     IntegerVector tmp(nn, 2.0);
     ComplexVector tmp1(tmp);
     x = x * tmp1;
@@ -117,7 +117,7 @@ ComplexVector complex_INTSXP( SEXP vec ){
 // [[Rcpp::export]]
 ComplexVector complex_REALSXP(SEXP vec){
     ComplexVector x(vec);
-    int nn = x.size();
+    R_xlen_t nn = x.size();
     NumericVector tmp(nn, 3.0);
     ComplexVector tmp1(tmp);
     x = x * tmp1;
@@ -165,7 +165,7 @@ IntegerVector integer_range_ctor_1(){
 // [[Rcpp::export]]
 IntegerVector integer_range_ctor_2(){
     std::vector<int> vec(4) ;
-    for( size_t i = 0; i<4; i++) vec[i] = i;
+    for( size_t i = 0; i<4; i++) vec[i] = static_cast<int>(i);
     IntegerVector y( vec.begin(), vec.end() ) ;
     return y;
 }
@@ -281,7 +281,7 @@ List integer_create_(){
 IntegerVector integer_clone_( IntegerVector vec ){
     IntegerVector dolly = clone( vec ) ;
     for( size_t i=0; i<10; i++){
-        dolly[i] = 10 - i ;
+        dolly[i] = static_cast<int>(10 - i) ;
     }
     return dolly ;
 }
@@ -622,7 +622,7 @@ List character_listOf( List ll ){
 // [[Rcpp::export]]
 int character_find_(CharacterVector y){
     CharacterVector::iterator it = std::find( y.begin(), y.end(), "foo" ) ;
-    return std::distance( y.begin(), it );
+    return static_cast<int>(std::distance( y.begin(), it ));
 }
 
 // [[Rcpp::export]]
@@ -671,9 +671,9 @@ bool containsElementNamed( List l, CharacterVector n){
 
 // [[Rcpp::export]]
 List CharacterVectorEqualityOperator( CharacterVector x, CharacterVector y){
-    int n = x.size() ;
+    R_xlen_t n = x.size() ;
     LogicalVector eq(n), neq(n);
-    for( int i=0; i<n; i++){
+    for( R_xlen_t i=0; i<n; i++){
         eq[i]  = x[i] == y[i] ;
         neq[i] = x[i] != y[i] ;
     }
@@ -687,42 +687,42 @@ List List_rep_ctor(IntegerVector x){
 
 // [[Rcpp::export]]
 int stdVectorDouble(std::vector<double> x) {
-    return x.size();
+    return static_cast<int>(x.size());
 }
 
 // [[Rcpp::export]]
 int stdVectorDoubleConst(const std::vector<double> x) {
-    return x.size();
+    return static_cast<int>(x.size());
 }
 
 // [[Rcpp::export]]
 int stdVectorDoubleRef(std::vector<double> & x) {
-    return x.size();
+    return static_cast<int>(x.size());
 }
 
 // [[Rcpp::export]]
 int stdVectorDoubleConstRef(const std::vector<double> & x) {
-    return x.size();
+    return static_cast<int>(x.size());
 }
 
 // [[Rcpp::export]]
 int stdVectorInt(std::vector<int> x) {
-    return x.size();
+    return static_cast<int>(x.size());
 }
 
 // [[Rcpp::export]]
 int stdVectorIntConst(const std::vector<int> x) {
-    return x.size();
+    return static_cast<int>(x.size());
 }
 
 // [[Rcpp::export]]
 int stdVectorIntRef(std::vector<int> & x) {
-    return x.size();
+    return static_cast<int>(x.size());
 }
 
 // [[Rcpp::export]]
 int stdVectorIntConstRef(const std::vector<int> & x) {
-    return x.size();
+    return static_cast<int>(x.size());
 }
 
 // [[Rcpp::export]]
@@ -808,7 +808,7 @@ void no_op(int major) {
 
 // [[Rcpp::export]]
 int noprotect_vector( Vector<REALSXP, NoProtectStorage> x){
-  return x.size() ;
+  return static_cast<int>(x.size()) ;
 }
 
 // [[Rcpp::export]]
@@ -850,7 +850,7 @@ IntegerVector vec_subset(IntegerVector x, IntegerVector y) {
 // [[Rcpp::export]]
 int CharacterVectorNoProtect(Vector<STRSXP, NoProtectStorage> s){
     s[0] = "";
-    return s.size();
+    return static_cast<int>(s.size());
 }
 
 // [[Rcpp::export]]
diff --git a/inst/tinytest/cpp/dates.cpp b/inst/tinytest/cpp/dates.cpp
index a175cc32f..92d306d07 100644
--- a/inst/tinytest/cpp/dates.cpp
+++ b/inst/tinytest/cpp/dates.cpp
@@ -2,6 +2,7 @@
 // dates.cpp: Rcpp R/C++ interface class library -- Date + Datetime tests
 //
 // Copyright (C) 2010 - 2025   Dirk Eddelbuettel and Romain Francois
+// Copyright (C) 2026          Dirk Eddelbuettel, Romain Francois and Iñaki Ucar
 //
 // This file is part of Rcpp.
 //
@@ -205,7 +206,7 @@ Date gmtime_mktime(Date d) {
     tm.tm_mday  = d.getDay();
     tm.tm_mon   = d.getMonth() - 1;    // range 0 to 11
     tm.tm_year  = d.getYear() - baseYear;
-    time_t tmp = mktime00(tm);    // use mktime() replacement borrowed from R
+    time_t tmp = static_cast<time_t>(mktime00(tm));    // use mktime() replacement borrowed from R
 
     struct tm chk = *gmtime_(&tmp);
     Date newd(chk.tm_year, chk.tm_mon + 1, chk.tm_mday);
@@ -221,7 +222,7 @@ double test_mktime(Date d) {
     tm.tm_mday  = d.getDay();
     tm.tm_mon   = d.getMonth() - 1;    // range 0 to 11
     tm.tm_year  = d.getYear() - baseYear;
-    time_t t = mktime00(tm);    // use mktime() replacement borrowed from R
+    time_t t = static_cast<time_t>(mktime00(tm));    // use mktime() replacement borrowed from R
     return static_cast<double>(t);
 }
 
diff --git a/inst/tinytest/cpp/language.cpp b/inst/tinytest/cpp/language.cpp
index 68aa58fe4..11d332981 100644
--- a/inst/tinytest/cpp/language.cpp
+++ b/inst/tinytest/cpp/language.cpp
@@ -2,7 +2,8 @@
 //
 // language.cpp: Rcpp R/C++ interface class library -- Language unit tests
 //
-// Copyright (C) 2012 Dirk Eddelbuettel and Romain Francois
+// Copyright (C) 2012 - 2025 Dirk Eddelbuettel and Romain Francois
+// Copyright (C) 2026        Dirk Eddelbuettel, Romain Francois and Iñaki Ucar
 //
 // This file is part of Rcpp.
 //
@@ -205,7 +206,7 @@ int runit_pl_size(){
 	p.push_back( 1 ) ;
 	p.push_back( 10.0 ) ;
 	p.push_back( 20.0 ) ;
-	return p.size() ;
+	return static_cast<int>(p.size()) ;
 }
 
 // [[Rcpp::export]]
diff --git a/src/date.cpp b/src/date.cpp
index ae6f30fe6..8ae2ca44c 100644
--- a/src/date.cpp
+++ b/src/date.cpp
@@ -1,6 +1,7 @@
 // Date.cpp: Rcpp R/C++ interface class library -- Date type
 //
-// Copyright (C) 2010 - 2023  Dirk Eddelbuettel and Romain Francois
+// Copyright (C) 2010 - 2025 Dirk Eddelbuettel and Romain Francois
+// Copyright (C) 2026        Dirk Eddelbuettel, Romain Francois and Iñaki Ucar
 //
 //    The mktime00() as well as the gmtime_() replacement function are
 //    Copyright (C) 2000 - 2010  The R Development Core Team.
@@ -821,7 +822,7 @@ struct tzhead {
 	    */
 	    if (u.tzhead.tzh_version[0] == '\0')
 		break;
-	    nread -= p - u.buf;
+	    nread -= (int)(p - u.buf);
 	    for (i = 0; i < nread; ++i)
 		u.buf[i] = p[i];
 	    /*
@@ -1184,7 +1185,7 @@ struct tzhead {
         }
         sp->charcnt = (int)(stdlen + 1);
         if (dstlen != 0)
-            sp->charcnt += dstlen + 1;
+            sp->charcnt += (int)(dstlen + 1);
         if ((size_t) sp->charcnt > sizeof sp->chars)
             return -1;
         cp = sp->chars;