diff --git a/voltha/adapters/device_handler.py b/voltha/adapters/device_handler.py
index 33bbd35..54f1106 100644
--- a/voltha/adapters/device_handler.py
+++ b/voltha/adapters/device_handler.py
@@ -44,6 +44,7 @@
     def __init__(self, adapter, device_id):
         super(OltDeviceHandler, self).__init__(adapter, device_id)
         self.filter = None
+        self.io_port = None
 
     def __del__(self):
         if self.io_port is not None: