--- a/ping6.c
+++ b/ping6.c
@@ -66,6 +66,8 @@ char copyright[] =
  *	More statistics could always be gathered.
  *	This program has to run SUID to ROOT to access the ICMP socket.
  */
+
+#define _GNU_SOURCE
 #include "ping_common.h"
 
 #include <linux/filter.h>
