diff --git a/iwf/registry.py b/iwf/registry.py
index 7317f20..dc4cb0c 100644
--- a/iwf/registry.py
+++ b/iwf/registry.py
@@ -85,7 +85,7 @@ def _register_workflow_type(self, wf: ObjectWorkflow):
     def _register_internal_channels(self, wf: ObjectWorkflow):
         wf_type = get_workflow_type(wf)
 
-        if self._internal_channel_type_store[wf_type] is None:
+        if wf_type not in self._internal_channel_type_store:
             self._internal_channel_type_store[wf_type] = TypeStore(
                 Type.INTERNAL_CHANNEL
             )