diff --git a/wally/openstack.py b/wally/openstack.py
index 5541d4c..3b5ced5 100644
--- a/wally/openstack.py
+++ b/wally/openstack.py
@@ -1,7 +1,7 @@
 import os.path
 import socket
 import logging
-from typing import Dict, Any, List, Tuple, cast
+from typing import Dict, Any, List, Tuple, cast, Optional
 
 from .node_interfaces import NodeInfo
 from .config import ConfigBlock, Config