diff --git a/include/nana/filesystem/filesystem.hpp b/include/nana/filesystem/filesystem.hpp
index 36f8776d..8aab0cea 100644
--- a/include/nana/filesystem/filesystem.hpp
+++ b/include/nana/filesystem/filesystem.hpp
@@ -560,7 +560,7 @@ namespace std {
 #endif
 	}
 } // std
-#else
+#else //#if NANA_USING_NANA_FILESYSTEM
 //Implements the missing functions for various version of experimental/filesystem
 	namespace std
 	{
@@ -568,7 +568,7 @@ namespace std {
 		{
 			//Visual Studio 2017
 #if			(defined(NANA_USING_STD_EXPERIMENTAL_FILESYSTEM) && defined(_MSC_VER) && (_MSC_VER > 1912)) ||	\
-				(!defined(__clang__) && defined(__GNUC__) && (__cplusplus < 201603))
+				(!defined(__clang__) && defined(__GNUC__) && (__cplusplus < 201603 || (__GNUC__* 100 + __GNUC_MINOR__ < 801)))
 			path weakly_canonical(const path& p);
 			path weakly_canonical(const path& p, std::error_code& err);
 #endif
diff --git a/source/filesystem/filesystem.cpp b/source/filesystem/filesystem.cpp
index ae812104..bcd5957c 100644
--- a/source/filesystem/filesystem.cpp
+++ b/source/filesystem/filesystem.cpp
@@ -1407,7 +1407,7 @@ namespace std
 		namespace filesystem
 		{
 #if		(defined(NANA_USING_STD_EXPERIMENTAL_FILESYSTEM) && defined(_MSC_VER) && (_MSC_VER > 1912)) ||	\
-			(!defined(__clang__) && defined(__GNUC__) && (__cplusplus < 201603))
+			(!defined(__clang__) && defined(__GNUC__) && (__cplusplus < 201603 || (__GNUC__* 100 + __GNUC_MINOR__ < 801)))
 
 			namespace detail
 			{