1 files changed, 6 insertions, 3 deletions
diff --git a/synapse/handlers/room_member.py b/synapse/handlers/room_member.py
index cac76d0221..27e2903a8f 100644
--- a/synapse/handlers/room_member.py
+++ b/synapse/handlers/room_member.py
@@ -678,7 +678,8 @@ class RoomMemberHandler(metaclass=abc.ABCMeta):
             if block_invite:
                 raise SynapseError(403, "Invites have been disabled on this server")
 
-        if prev_event_ids:
+        # An empty prev_events list is allowed as long as the auth_event_ids are present
+        if prev_event_ids is not None:
             return await self._local_membership_update(
                 requester=requester,
                 target=target,
@@ -1039,7 +1040,7 @@ class RoomMemberHandler(metaclass=abc.ABCMeta):
         # Add new room to the room directory if the old room was there
         # Remove old room from the room directory
         old_room = await self.store.get_room(old_room_id)
-        if old_room and old_room["is_public"]:
+        if old_room is not None and old_room["is_public"]:
             await self.store.set_room_is_public(old_room_id, False)
             await self.store.set_room_is_public(room_id, True)
 
@@ -1050,7 +1051,9 @@ class RoomMemberHandler(metaclass=abc.ABCMeta):
         local_group_ids = await self.store.get_local_groups_for_room(old_room_id)
         for group_id in local_group_ids:
             # Add new the new room to those groups
-            await self.store.add_room_to_group(group_id, room_id, old_room["is_public"])
+            await self.store.add_room_to_group(
+                group_id, room_id, old_room is not None and old_room["is_public"]
+            )
 
             # Remove the old room from those groups
             await self.store.remove_room_from_group(group_id, old_room_id)