diff --git a/Xosdefs.h b/Xosdefs.h
index 075d798..be90d5e 100644
--- a/Xosdefs.h
+++ b/Xosdefs.h
@@ -133,7 +133,7 @@ in this Software without prior written authorization from The Open Group.
 #define NULL_NOT_ZERO
 #endif
 
-#ifdef __DARWIN__
+#ifdef __APPLE__
 #define NULL_NOT_ZERO
 #endif