diff --git a/untie.c b/untie.c
index f08a10d..d3d20b4 100644
--- a/untie.c
+++ b/untie.c
@@ -18,6 +18,7 @@
  * Copyright (c) 2006, 2007 Guillaume Chazarain <guichaz@yahoo.fr>
  */
 
+#define _GNU_SOURCE
 #include <sys/time.h>
 #include <sys/resource.h>
 #include <sys/wait.h>