diff --git a/include/net/protocol.h b/include/net/protocol.h
index 28c4cac..105bf12 100644
--- a/include/net/protocol.h
+++ b/include/net/protocol.h
@@ -71,7 +71,7 @@
 
         /* These two fields form the lookup key.  */
 	unsigned short	 type;	   /* This is the 2nd argument to socket(2). */
-	int		 protocol; /* This is the L4 protocol number.  */
+	unsigned short	 protocol; /* This is the L4 protocol number.  */
 
 	struct proto	 *prot;
 	const struct proto_ops *ops;