diff --git a/include/nlohmann/detail/input/lexer.hpp b/include/nlohmann/detail/input/lexer.hpp
index b18893a4d..5c9d5ed5c 100644
--- a/include/nlohmann/detail/input/lexer.hpp
+++ b/include/nlohmann/detail/input/lexer.hpp
@@ -936,7 +936,7 @@ class lexer : public lexer_base<BasicJsonType>
 
         while (*p >= '0' and * p <= '9')
         {
-            val = (10 * val) + (*p - '0');
+            val = (10U * val) + static_cast<number_unsigned_t>((*p - '0'));
             p++;
         }
 
diff --git a/single_include/nlohmann/json.hpp b/single_include/nlohmann/json.hpp
index 18ec30246..b04619fe1 100644
--- a/single_include/nlohmann/json.hpp
+++ b/single_include/nlohmann/json.hpp
@@ -9048,7 +9048,7 @@ class lexer : public lexer_base<BasicJsonType>
 
         while (*p >= '0' and * p <= '9')
         {
-            val = (10 * val) + (*p - '0');
+            val = (10U * val) + static_cast<number_unsigned_t>((*p - '0'));
             p++;
         }