diff --git a/libc/kernel/uapi/linux/sysctl.h b/libc/kernel/uapi/linux/sysctl.h
index ae9c2ba..ff17f7c 100644
--- a/libc/kernel/uapi/linux/sysctl.h
+++ b/libc/kernel/uapi/linux/sysctl.h
@@ -516,6 +516,7 @@
   NET_NEIGH_GC_THRESH3 = 16,
   NET_NEIGH_RETRANS_TIME_MS = 17,
   NET_NEIGH_REACHABLE_TIME_MS = 18,
+  NET_NEIGH_INTERVAL_PROBE_TIME_MS = 19,
 };
 enum {
   NET_DCCP_DEFAULT = 1,