diff --git a/sbin/reboot/reboot.c b/sbin/reboot/reboot.c
index 87abb651744..28b84ff25bc 100644
--- a/sbin/reboot/reboot.c
+++ b/sbin/reboot/reboot.c
@@ -116,6 +116,8 @@ main(int argc, char *argv[])
 		}
 	argc -= optind;
 	argv += optind;
+	if (argc != 0)
+		usage();
 
 	if ((howto & (RB_DUMP | RB_HALT)) == (RB_DUMP | RB_HALT))
 		errx(1, "cannot dump (-d) when halting; must reboot instead");