1 files changed, 2 insertions, 3 deletions
diff --git a/synapse/util/async_helpers.py b/synapse/util/async_helpers.py
index 96efc5f3e3..561b962e14 100644
--- a/synapse/util/async_helpers.py
+++ b/synapse/util/async_helpers.py
@@ -31,13 +31,13 @@ from typing import (
     Set,
     TypeVar,
     Union,
+    cast,
 )
 
 import attr
 from typing_extensions import ContextManager
 
 from twisted.internet import defer
-from twisted.internet.base import ReactorBase
 from twisted.internet.defer import CancelledError
 from twisted.internet.interfaces import IReactorTime
 from twisted.python import failure
@@ -271,8 +271,7 @@ class Linearizer:
         if not clock:
             from twisted.internet import reactor
 
-            assert isinstance(reactor, ReactorBase)
-            clock = Clock(reactor)
+            clock = Clock(cast(IReactorTime, reactor))
         self._clock = clock
         self.max_count = max_count