diff --git a/include/nlohmann/detail/iterators/iteration_proxy.hpp b/include/nlohmann/detail/iterators/iteration_proxy.hpp
index 8c54746f6..c61d96296 100644
--- a/include/nlohmann/detail/iterators/iteration_proxy.hpp
+++ b/include/nlohmann/detail/iterators/iteration_proxy.hpp
@@ -13,7 +13,7 @@ namespace nlohmann
 namespace detail
 {
 template<typename string_type>
-void int_to_string( string_type& target, int value )
+void int_to_string( string_type& target, std::size_t value )
 {
     target = std::to_string(value);
 }
diff --git a/single_include/nlohmann/json.hpp b/single_include/nlohmann/json.hpp
index 10a48c1dd..e680d8b7d 100644
--- a/single_include/nlohmann/json.hpp
+++ b/single_include/nlohmann/json.hpp
@@ -3277,7 +3277,7 @@ namespace nlohmann
 namespace detail
 {
 template<typename string_type>
-void int_to_string( string_type& target, int value )
+void int_to_string( string_type& target, std::size_t value )
 {
     target = std::to_string(value);
 }
diff --git a/test/src/unit-alt-string.cpp b/test/src/unit-alt-string.cpp
index 57ddc83a3..51a882179 100644
--- a/test/src/unit-alt-string.cpp
+++ b/test/src/unit-alt-string.cpp
@@ -154,7 +154,7 @@ class alt_string
     friend bool ::operator<(const char*, const alt_string&);
 };
 
-void int_to_string( alt_string& target, int value )
+void int_to_string( alt_string& target, std::size_t value )
 {
     target = std::to_string(value).c_str();
 }