$OpenBSD$
--- io.c.orig	Thu Dec 22 17:30:58 2005
+++ io.c	Thu Dec 22 17:30:58 2005
@@ -17,7 +17,6 @@
 # include "config.h"
 #endif
 
-#define _XOPEN_SOURCE   600 /* we need the POSIX version of strerror_r() */
 
 #include <stdlib.h>
 #include <sys/types.h>
