diff --git a/include/linux/sysctl.h b/include/linux/sysctl.h
index bac61db..0f49413 100644
--- a/include/linux/sysctl.h
+++ b/include/linux/sysctl.h
@@ -531,6 +531,7 @@
 	NET_IPV6_MAX_DESYNC_FACTOR=15,
 	NET_IPV6_MAX_ADDRESSES=16,
 	NET_IPV6_FORCE_MLD_VERSION=17,
+	NET_IPV6_ACCEPT_RA_DEFRTR=18,
 	__NET_IPV6_MAX
 };