diff --git a/mednafen/sound/Blip_Buffer.c b/mednafen/sound/Blip_Buffer.c
index f8c8375..5f4c127 100644
--- a/mednafen/sound/Blip_Buffer.c
+++ b/mednafen/sound/Blip_Buffer.c
@@ -8,6 +8,10 @@
 #include <stdlib.h>
 #include <math.h>
 
+#ifndef ULLONG_MAX
+#define ULLONG_MAX 18446744073709551615ULL
+#endif
+
 /* Copyright (C) 2003-2006 Shay Green. This module is free software; you
 can redistribute it and/or modify it under the terms of the GNU Lesser
 General Public License as published by the Free Software Foundation; either