diff --git a/arch/sandbox/cpu/eth-raw-os.c b/arch/sandbox/cpu/eth-raw-os.c
index 6a8d809..e59b96b 100644
--- a/arch/sandbox/cpu/eth-raw-os.c
+++ b/arch/sandbox/cpu/eth-raw-os.c
@@ -4,6 +4,8 @@
  * Copyright (c) 2015-2018 Joe Hershberger <joe.hershberger@ni.com>
  */
 
+#define _GNU_SOURCE
+
 #include <asm/eth-raw-os.h>
 #include <errno.h>
 #include <fcntl.h>