1 files changed, 4 insertions, 1 deletions

diff --git a/src/mailman/rest/helpers.py b/src/mailman/rest/helpers.py
index 0cdd40e7e..e20324cfd 100644
--- a/src/mailman/rest/helpers.py
+++ b/src/mailman/rest/helpers.py
@@ -134,7 +134,9 @@ class CollectionMixin:
 
     def _resource_as_json(self, resource):
         """Return the JSON formatted representation of the resource."""
-        return etag(self._resource_as_dict(resource))
+        resource = self._resource_as_dict(resource)
+        assert resource is not None, resource
+        return etag(resource)
 
     def _get_collection(self, request):
         """Return the collection as a concrete list.
@@ -175,6 +177,7 @@ class CollectionMixin:
         if len(collection) != 0:
             entries = [self._resource_as_dict(resource)
                        for resource in collection]
+            assert None not in entries, entries
             # Tag the resources but use the dictionaries.
             [etag(resource) for resource in entries]
             # Create the collection resource