diff --git a/include/magic_enum.hpp b/include/magic_enum.hpp
index 1320d4e..a2d7bdf 100644
--- a/include/magic_enum.hpp
+++ b/include/magic_enum.hpp
@@ -45,6 +45,7 @@
 
 // Checks magic_enum compiler compatibility.
 #if defined(__clang__) || defined(__GNUC__) && __GNUC__>= 9 || defined(_MSC_VER)
+#  undef MAGIC_ENUM_SUPPORTED
 #  define MAGIC_ENUM_SUPPORTED 1
 #endif