1 files changed, 1 insertions, 1 deletions
diff --git a/synapse/push/bulk_push_rule_evaluator.py b/synapse/push/bulk_push_rule_evaluator.py
index 8140afcb6b..030898e4d0 100644
--- a/synapse/push/bulk_push_rule_evaluator.py
+++ b/synapse/push/bulk_push_rule_evaluator.py
@@ -213,7 +213,7 @@ class BulkPushRuleEvaluator:
         if not event.is_state():
             ignorers = await self.store.ignored_by(event.sender)
         else:
-            ignorers = set()
+            ignorers = frozenset()
 
         for uid, rules in rules_by_user.items():
             if event.sender == uid: