diff --git a/include/ghc/filesystem.hpp b/include/ghc/filesystem.hpp
index 913c36d..2bc0560 100644
--- a/include/ghc/filesystem.hpp
+++ b/include/ghc/filesystem.hpp
@@ -95,27 +95,47 @@
 #define GHC_EXPAND_IMPL
 #define GHC_INLINE
 #ifdef GHC_OS_WINDOWS
+#ifndef GHC_FS_API
 #define GHC_FS_API
+#endif
+#ifndef GHC_FS_API_CLASS
 #define GHC_FS_API_CLASS
+#endif
 #else
+#ifndef GHC_FS_API
 #define GHC_FS_API __attribute__((visibility("default")))
+#endif
+#ifndef GHC_FS_API_CLASS
 #define GHC_FS_API_CLASS __attribute__((visibility("default")))
 #endif
+#endif
 #elif defined(GHC_FILESYSTEM_FWD)
 #define GHC_INLINE
 #ifdef GHC_OS_WINDOWS
+#ifndef GHC_FS_API
 #define GHC_FS_API extern
+#endif
+#ifndef GHC_FS_API_CLASS
 #define GHC_FS_API_CLASS
+#endif
 #else
+#ifndef GHC_FS_API
 #define GHC_FS_API extern
+#endif
+#ifndef GHC_FS_API_CLASS
 #define GHC_FS_API_CLASS
 #endif
+#endif
 #else
 #define GHC_EXPAND_IMPL
 #define GHC_INLINE inline
+#ifndef GHC_FS_API
 #define GHC_FS_API
+#endif
+#ifndef GHC_FS_API_CLASS
 #define GHC_FS_API_CLASS
 #endif
+#endif
 
 #ifdef GHC_EXPAND_IMPL