diff --git a/inet/netinet/in.h b/inet/netinet/in.h
index f684be5beb..29fdd9b85e 100644
--- a/inet/netinet/in.h
+++ b/inet/netinet/in.h
@@ -93,6 +93,8 @@ enum
 #define IPPROTO_ETHERNET	IPPROTO_ETHERNET
     IPPROTO_RAW = 255,	   /* Raw IP packets.  */
 #define IPPROTO_RAW		IPPROTO_RAW
+    IPPROTO_SMC = 256,	   /* Shared Memory Communications.  */
+#define IPPROTO_SMC		IPPROTO_SMC
     IPPROTO_MPTCP = 262,   /* Multipath TCP connection.  */
 #define IPPROTO_MPTCP		IPPROTO_MPTCP
     IPPROTO_MAX