diff --git a/testcase.c b/testcase.c
--- a/testcase.c
+++ b/testcase.c
@@ -3,7 +3,7 @@
  * Copyright (C) 2008 Markus Broeker
  */
 
-#define _XOPEN_SOURCE 500
+#define _XOPEN_SOURCE 600
 
 #include <stdio.h>
 #include <stdlib.h>