1 files changed, 2 insertions, 1 deletions
diff --git a/synapse/handlers/message.py b/synapse/handlers/message.py
index 95a89ac01f..c28b792e6f 100644
--- a/synapse/handlers/message.py
+++ b/synapse/handlers/message.py
@@ -1427,7 +1427,7 @@ class EventCreationHandler:
             # Validate a newly added alias or newly added alt_aliases.
 
             original_alias = None
-            original_alt_aliases: List[str] = []
+            original_alt_aliases: object = []
 
             original_event_id = event.unsigned.get("replaces_state")
             if original_event_id:
@@ -1455,6 +1455,7 @@ class EventCreationHandler:
             # If the old version of alt_aliases is of an unknown form,
             # completely replace it.
             if not isinstance(original_alt_aliases, (list, tuple)):
+                # TODO: check that the original_alt_aliases' entries are all strings
                 original_alt_aliases = []
 
             # Check that each alias is currently valid.