diff --git a/libc/kernel/uapi/linux/in6.h b/libc/kernel/uapi/linux/in6.h
index 9da111c..3627f52 100644
--- a/libc/kernel/uapi/linux/in6.h
+++ b/libc/kernel/uapi/linux/in6.h
@@ -132,6 +132,7 @@
 #define IPV6_V6ONLY 26
 #define IPV6_JOIN_ANYCAST 27
 #define IPV6_LEAVE_ANYCAST 28
+#define IPV6_MULTICAST_ALL 29
 #define IPV6_PMTUDISC_DONT 0
 #define IPV6_PMTUDISC_WANT 1
 #define IPV6_PMTUDISC_DO 2