diff --git a/include/linux/sysctl.h b/include/linux/sysctl.h
index 236f537..f49488f 100644
--- a/include/linux/sysctl.h
+++ b/include/linux/sysctl.h
@@ -534,6 +534,7 @@
 	NET_IPV6_ACCEPT_RA_DEFRTR=18,
 	NET_IPV6_ACCEPT_RA_PINFO=19,
 	NET_IPV6_ACCEPT_RA_RTR_PREF=20,
+	NET_IPV6_RTR_PROBE_INTERVAL=21,
 	__NET_IPV6_MAX
 };