diff --git a/mio/lib/mio-prv.h b/mio/lib/mio-prv.h
index 9a0259d..d592402 100644
--- a/mio/lib/mio-prv.h
+++ b/mio/lib/mio-prv.h
@@ -59,7 +59,7 @@
 
 #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