diff --git a/common.c b/common.c
index 25bf761..26be47f 100644
--- a/common.c
+++ b/common.c
@@ -19,7 +19,7 @@
  */
 
 #define _POSIX_C_SOURCE 199309L
-#define _XOPEN_SOURCE 500
+#define _XOPEN_SOURCE 600
 
 #include <stdio.h>
 #include <stdlib.h>