diff --git a/libc/kernel/uapi/linux/sysctl.h b/libc/kernel/uapi/linux/sysctl.h
index 3f53f2d..ebaf8a9 100644
--- a/libc/kernel/uapi/linux/sysctl.h
+++ b/libc/kernel/uapi/linux/sysctl.h
@@ -489,6 +489,7 @@
   NET_IPV6_ACCEPT_SOURCE_ROUTE = 25,
   NET_IPV6_ACCEPT_RA_FROM_LOCAL = 26,
   NET_IPV6_ACCEPT_RA_RT_INFO_MIN_PLEN = 27,
+  NET_IPV6_RA_DEFRTR_METRIC = 28,
   __NET_IPV6_MAX
 };
 enum {