diff --git a/feed/mwctl/src/main.c b/feed/mwctl/src/main.c
index e2421f2..af7b31e 100755
--- a/feed/mwctl/src/main.c
+++ b/feed/mwctl/src/main.c
@@ -80,7 +80,13 @@
 
 	progname = argv[0];
 
-	if_idx = if_nametoindex(argv[1]);
+	if(argv[1])
+		if_idx = if_nametoindex(argv[1]);
+	else {
+		fprintf(stderr, "wrong argument\n");
+		usage();
+	}
+
 	if (!if_idx) {
 		fprintf(stderr, "%s\n", strerror(errno));
 		return 2;