diff --git a/synapse/http/server.py b/synapse/http/server.py
index f19c0c4f2d..0ba427faf6 100644
--- a/synapse/http/server.py
+++ b/synapse/http/server.py
@@ -331,7 +331,9 @@ class _AsyncResource(resource.Resource, metaclass=abc.ABCMeta):
 
     def render(self, request: SynapseRequest) -> int:
         """This gets called by twisted every time someone sends us a request."""
-        defer.ensureDeferred(self._async_render_wrapper(request))
+        request.render_deferred = defer.ensureDeferred(
+            self._async_render_wrapper(request)
+        )
         return NOT_DONE_YET
 
     @wrap_async_request_handler