diff --git a/tools/helpers/xen-init-dom0.c b/tools/helpers/xen-init-dom0.c
index 37eff8868f..764f837887 100644
--- a/tools/helpers/xen-init-dom0.c
+++ b/tools/helpers/xen-init-dom0.c
@@ -1,3 +1,5 @@
+#define _GNU_SOURCE
+
 #include <stdlib.h>
 #include <stdint.h>
 #include <string.h>