diff --git a/federationapi/routing/send.go b/federationapi/routing/send.go
index a514127c..59753e15 100644
--- a/federationapi/routing/send.go
+++ b/federationapi/routing/send.go
@@ -625,14 +625,9 @@ func checkAllowedByState(e *gomatrixserverlib.Event, stateEvents []*gomatrixserv
 	return gomatrixserverlib.Allowed(e, &authUsingState)
 }
 
-var processEventWithMissingStateMutexes = internal.NewMutexByRoom()
-
 func (t *txnReq) processEventWithMissingState(
 	ctx context.Context, e *gomatrixserverlib.Event, roomVersion gomatrixserverlib.RoomVersion,
 ) error {
-	processEventWithMissingStateMutexes.Lock(e.RoomID())
-	defer processEventWithMissingStateMutexes.Unlock(e.RoomID())
-
 	// Do this with a fresh context, so that we keep working even if the
 	// original request times out. With any luck, by the time the remote
 	// side retries, we'll have fetched the missing state.