1 files changed, 7 insertions, 1 deletions
diff --git a/synapse/handlers/message.py b/synapse/handlers/message.py
index 8b27e23378..e951c39fa7 100644
--- a/synapse/handlers/message.py
+++ b/synapse/handlers/message.py
@@ -378,7 +378,11 @@ class EventCreationHandler(object):
             # tolerate them in event_auth.check().
             prev_state_ids = yield context.get_prev_state_ids(self.store)
             prev_event_id = prev_state_ids.get((EventTypes.Member, event.sender))
-            prev_event = yield self.store.get_event(prev_event_id, allow_none=True)
+            prev_event = (
+                yield self.store.get_event(prev_event_id, allow_none=True)
+                if prev_event_id
+                else None
+            )
             if not prev_event or prev_event.membership != Membership.JOIN:
                 logger.warning(
                     (
@@ -521,6 +525,8 @@ class EventCreationHandler(object):
         """
         prev_state_ids = yield context.get_prev_state_ids(self.store)
         prev_event_id = prev_state_ids.get((event.type, event.state_key))
+        if not prev_event_id:
+            return
         prev_event = yield self.store.get_event(prev_event_id, allow_none=True)
         if not prev_event:
             return