diff --git a/common/cmd_mii.c b/common/cmd_mii.c
index f530a3842..079612a4e 100644
--- a/common/cmd_mii.c
+++ b/common/cmd_mii.c
@@ -438,6 +438,11 @@ int do_mii (cmd_tbl_t * cmdtp, int flag, int argc, char *argv[])
 	int		rcode = 0;
 	char		*devname;
 
+	if (argc < 2) {
+		printf("Usage:\n%s\n", cmdtp->usage);
+		return 1;
+	}
+
 #if defined(CONFIG_8xx) || defined(CONFIG_MCF532x)
 	mii_init ();
 #endif