diff --git a/libc/kernel/uapi/linux/nbd-netlink.h b/libc/kernel/uapi/linux/nbd-netlink.h
index 9faf689..dffb077 100644
--- a/libc/kernel/uapi/linux/nbd-netlink.h
+++ b/libc/kernel/uapi/linux/nbd-netlink.h
@@ -32,6 +32,7 @@
   NBD_ATTR_SOCKETS,
   NBD_ATTR_DEAD_CONN_TIMEOUT,
   NBD_ATTR_DEVICE_LIST,
+  NBD_ATTR_BACKEND_IDENTIFIER,
   __NBD_ATTR_MAX,
 };
 #define NBD_ATTR_MAX (__NBD_ATTR_MAX - 1)