1 files changed, 3 insertions, 1 deletions
diff --git a/synapse/http/server.py b/synapse/http/server.py
index 211795dc39..0d0c610b28 100644
--- a/synapse/http/server.py
+++ b/synapse/http/server.py
@@ -74,6 +74,7 @@ from synapse.api.errors import (
 from synapse.config.homeserver import HomeServerConfig
 from synapse.logging.context import defer_to_thread, preserve_fn, run_in_background
 from synapse.logging.opentracing import active_span, start_active_span, trace_servlet
+from synapse.types import ISynapseReactor
 from synapse.util import json_encoder
 from synapse.util.caches import intern_dict
 from synapse.util.cancellation import is_function_cancellable
@@ -868,7 +869,8 @@ async def _async_write_json_to_request_in_thread(
 
     with start_active_span("encode_json_response"):
         span = active_span()
-        json_str = await defer_to_thread(request.reactor, encode, span)
+        reactor: ISynapseReactor = request.reactor  # type: ignore
+        json_str = await defer_to_thread(reactor, encode, span)
 
     _write_bytes_to_request(request, json_str)