diff --git a/src/fmt/print.c b/src/fmt/print.c
index 232a230..87cd1be 100644
--- a/src/fmt/print.c
+++ b/src/fmt/print.c
@@ -3,6 +3,7 @@
  *
  * Copyright (C) 2010 Creytiv.com
  */
+#define _GNU_SOURCE 1
 #include <string.h>
 #include <re_types.h>
 #include <re_sa.h>