diff --git a/moo/lib/moo-prv.h b/moo/lib/moo-prv.h
index 95a058a..0254c72 100644
--- a/moo/lib/moo-prv.h
+++ b/moo/lib/moo-prv.h
@@ -103,7 +103,7 @@
 
 #else
 
-#	if defined(HAVE___BUILTIN_MEMSET) || !defined(HAVE___BUILTIN_MEMCPY) || !defined(HAVE___BUILTIN_MEMMOVE) || !defined(HAVE___BUILTIN_MEMCMP)
+#	if !defined(HAVE___BUILTIN_MEMSET) || !defined(HAVE___BUILTIN_MEMCPY) || !defined(HAVE___BUILTIN_MEMMOVE) || !defined(HAVE___BUILTIN_MEMCMP)
 #	include <string.h>
 #	endif