diff --git a/include/nlohmann/detail/conversions/to_json.hpp b/include/nlohmann/detail/conversions/to_json.hpp
index e39b7797d..8a8610821 100644
--- a/include/nlohmann/detail/conversions/to_json.hpp
+++ b/include/nlohmann/detail/conversions/to_json.hpp
@@ -320,7 +320,14 @@ template<typename BasicJsonType, typename EnumType,
 inline void to_json(BasicJsonType& j, EnumType e) noexcept
 {
     using underlying_type = typename std::underlying_type<EnumType>::type;
-    external_constructor<value_t::number_integer>::construct(j, static_cast<underlying_type>(e));
+    if (std::is_unsigned<underlying_type>::value)
+    {
+        external_constructor<value_t::number_unsigned>::construct(j, static_cast<underlying_type>(e));
+    }
+    else
+    {
+        external_constructor<value_t::number_integer>::construct(j, static_cast<underlying_type>(e));
+    }
 }
 #endif  // JSON_DISABLE_ENUM_SERIALIZATION