diff --git a/quadbase.c b/quadbase.c
index 22735c7..7e29788 100644
--- a/quadbase.c
+++ b/quadbase.c
@@ -18,6 +18,10 @@ typedef HANDLE thread_id_t;
 #define mkdir(P,X)      _mkdir(P)
 #define S_IFDIR         _S_IFDIR
 
+#ifndef S_ISDIR
+#define S_ISDIR(mode) _S_ISTYPE((mode), _S_IFDIR)
+#endif
+
 #else
 
 #define USE_PTHREAD