diff --git a/sys/kern/uipc_socket.c b/sys/kern/uipc_socket.c
--- a/sys/kern/uipc_socket.c
+++ b/sys/kern/uipc_socket.c
@@ -3860,7 +3860,10 @@
 			break;
 
 		case SO_SETFIB:
-			error = so->so_proto->pr_ctloutput(so, sopt);
+			if (so->so_proto->pr_ctloutput != NULL)
+				error = so->so_proto->pr_ctloutput(so, sopt);
+			else
+				error = EPROTONOSUPPORT;
 			break;
 
 		case SO_USER_COOKIE: