diff --git a/run-docker b/run-docker
index b51136d..df3cfda 100755
--- a/run-docker
+++ b/run-docker
@@ -59,7 +59,7 @@ cmd_action_map = {
 }
 parser = argparse.ArgumentParser()
 parser.add_argument('--dry-run', default=False, action='store_true')
-parser.add_argument('cmd', choices=cmd_action_map)
+parser.add_argument('cmd', choices=cmd_action_map, default='sh', nargs='?')
 parser.add_argument('args', nargs='*')
 args = parser.parse_args()
 sh = shell_helpers.ShellHelpers(dry_run=args.dry_run)