diff --git a/httplib.h b/httplib.h
index f918aa5..250d4ca 100644
--- a/httplib.h
+++ b/httplib.h
@@ -29,7 +29,9 @@
 #define S_ISDIR(m)  (((m)&S_IFDIR)==S_IFDIR)
 #endif //S_ISDIR
 
+#ifndef NOMINMAX
 #define NOMINMAX
+#endif //NOMINMAX
 
 #include <io.h>
 #include <winsock2.h>