diff --git a/include/boost/charconv/detail/parser.hpp b/include/boost/charconv/detail/parser.hpp
index c260ae6a..585d760b 100644
--- a/include/boost/charconv/detail/parser.hpp
+++ b/include/boost/charconv/detail/parser.hpp
@@ -365,7 +365,7 @@ inline from_chars_result parser(const char* first, const char* last, bool& sign,
 
             if (round)
             {
-                significand += 1;
+                significand = static_cast<Unsigned_Integer>(significand + 1u);
             }
         }
         else