diff --git a/toml/parser.hpp b/toml/parser.hpp
index a52d8c9..f6d6374 100644
--- a/toml/parser.hpp
+++ b/toml/parser.hpp
@@ -13,12 +13,12 @@
 #include "types.hpp"
 #include "value.hpp"
 
-#if __cplusplus >= 201703L
+#ifdef __cpp_lib_filesystem
 #if __has_include(<filesystem>)
 #define TOML11_HAS_STD_FILESYSTEM
 #include <filesystem>
 #endif // has_include(<string_view>)
-#endif // cplusplus   >= C++17
+#endif // __cpp_lib_filesystem
 
 namespace toml
 {