diff --git a/include/outcome/convert.hpp b/include/outcome/convert.hpp
index 99cb8694bc..d9941a54bc 100644
--- a/include/outcome/convert.hpp
+++ b/include/outcome/convert.hpp
@@ -32,7 +32,7 @@ OUTCOME_V2_NAMESPACE_EXPORT_BEGIN
 namespace concepts
 {
 #if defined(__cpp_concepts)
-#if !defined(_MSC_VER) && !defined(__clang__) && (__GNUC__ < 9 || __cplusplus < 202000L)
+#if !defined(_MSC_VER) && !defined(__clang__) && (__GNUC__ < 9 || __cpp_concepts < 201907L)
 #define OUTCOME_GCC6_CONCEPT_BOOL bool
 #else
 #define OUTCOME_GCC6_CONCEPT_BOOL