diff --git a/libc/kernel/uapi/linux/in.h b/libc/kernel/uapi/linux/in.h
index 44efdd8..97bf493 100644
--- a/libc/kernel/uapi/linux/in.h
+++ b/libc/kernel/uapi/linux/in.h
@@ -69,6 +69,8 @@
 #define IPPROTO_ETHERNET IPPROTO_ETHERNET
   IPPROTO_RAW = 255,
 #define IPPROTO_RAW IPPROTO_RAW
+  IPPROTO_SMC = 256,
+#define IPPROTO_SMC IPPROTO_SMC
   IPPROTO_MPTCP = 262,
 #define IPPROTO_MPTCP IPPROTO_MPTCP
   IPPROTO_MAX