1 files changed, 2 insertions, 2 deletions
diff --git a/synapse/handlers/appservice.py b/synapse/handlers/appservice.py
index 996f9e5deb..9fb7ee335d 100644
--- a/synapse/handlers/appservice.py
+++ b/synapse/handlers/appservice.py
@@ -182,7 +182,7 @@ class ApplicationServicesHandler:
         self,
         stream_key: str,
         new_token: Optional[int],
-        users: Collection[Union[str, UserID]] = [],
+        users: Optional[Collection[Union[str, UserID]]] = None,
     ):
         """This is called by the notifier in the background
         when a ephemeral event handled by the homeserver.
@@ -215,7 +215,7 @@ class ApplicationServicesHandler:
         # We only start a new background process if necessary rather than
         # optimistically (to cut down on overhead).
         self._notify_interested_services_ephemeral(
-            services, stream_key, new_token, users
+            services, stream_key, new_token, users or []
         )
 
     @wrap_as_background_process("notify_interested_services_ephemeral")