diff --git a/include/linux/ipv6.h b/include/linux/ipv6.h
index ff56053..7121a2e 100644
--- a/include/linux/ipv6.h
+++ b/include/linux/ipv6.h
@@ -42,6 +42,7 @@
 	__s32		accept_ra_from_local;
 #ifdef CONFIG_IPV6_OPTIMISTIC_DAD
 	__s32		optimistic_dad;
+	__s32		use_optimistic;
 #endif
 #ifdef CONFIG_IPV6_MROUTE
 	__s32		mc_forwarding;