diff --git a/synapse/storage/databases/main/deviceinbox.py b/synapse/storage/databases/main/deviceinbox.py

index c55508867d..3154906d45 100644
--- a/synapse/storage/databases/main/deviceinbox.py
+++ b/synapse/storage/databases/main/deviceinbox.py
@@ -136,7 +136,7 @@ class DeviceInboxWorkerStore(SQLBaseStore):
             user_id, last_stream_id
         )
         if not has_changed:
-            return ([], current_stream_id)
+            return [], current_stream_id
 
         def get_new_messages_for_device_txn(txn):
             sql = (
@@ -240,11 +240,11 @@ class DeviceInboxWorkerStore(SQLBaseStore):
         )
         if not has_changed or last_stream_id == current_stream_id:
             log_kv({"message": "No new messages in stream"})
-            return ([], current_stream_id)
+            return [], current_stream_id
 
         if limit <= 0:
             # This can happen if we run out of room for EDUs in the transaction.
-            return ([], last_stream_id)
+            return [], last_stream_id
 
         @trace
         def get_new_messages_for_remote_destination_txn(txn):