diff --git a/swh/indexer/indexer.py b/swh/indexer/indexer.py
--- a/swh/indexer/indexer.py
+++ b/swh/indexer/indexer.py
@@ -622,9 +622,11 @@
     def process_journal_objects(self, objects: ObjectsDict) -> Dict:
         """Worker function for ``JournalClient``. Expects ``objects`` to have a single
         key, ``"directory"``."""
-        assert set(objects) == {"directory"}
         return self._process_directories(
-            [(dir_["id"], Directory.from_dict(dir_)) for dir_ in objects["directory"]]
+            [
+                (dir_["id"], Directory.from_dict(dir_))
+                for dir_ in objects.get("directory", [])
+            ]
         )
 
     def _process_directories(