diff --git a/bfd_packet.c b/bfd_packet.c
index e8f99f9..2c9fa91 100644
--- a/bfd_packet.c
+++ b/bfd_packet.c
@@ -29,6 +29,8 @@
 #define _UAPI_IPV6_H
 #endif /* _UAPI_IPV6_H */
 
+#define _GNU_SOURCE
+
 #include <linux/filter.h>
 #include <linux/if_ether.h>
 #include <linux/if_packet.h>