diff --git a/clientapi/routing/sendtodevice.go b/clientapi/routing/sendtodevice.go
index 45ea86c75..5d3060d74 100644
--- a/clientapi/routing/sendtodevice.go
+++ b/clientapi/routing/sendtodevice.go
@@ -33,13 +33,11 @@ func SendToDevice(
 	eventType string, txnID *string,
 ) util.JSONResponse {
 	if txnID != nil {
-		// Try to fetch response from transactionsCache
 		if res, ok := txnCache.FetchTransaction(device.AccessToken, *txnID); ok {
 			return *res
 		}
 	}
 
-	// parse the incoming http request
 	var httpReq struct {
 		Messages map[string]map[string]json.RawMessage `json:"messages"`
 	}
@@ -59,8 +57,14 @@ func SendToDevice(
 		}
 	}
 
-	return util.JSONResponse{
+	res := util.JSONResponse{
 		Code: http.StatusOK,
 		JSON: struct{}{},
 	}
+
+	if txnID != nil {
+		txnCache.AddTransaction(device.AccessToken, *txnID, &res)
+	}
+
+	return res
 }
diff --git a/syncapi/sync/requestpool.go b/syncapi/sync/requestpool.go
index 402ac5dcf..725952ed8 100644
--- a/syncapi/sync/requestpool.go
+++ b/syncapi/sync/requestpool.go
@@ -174,11 +174,9 @@ func (rp *RequestPool) currentSyncForUser(req syncRequest, latestPos types.Strea
 		// This is a bit of a hack until we can do something better with the sync API
 		// than this mess. If we have pending send-to-device updates then we want to
 		// deliver them pretty quickly. We still want the next step to run so that the
-		// sync tokens are updated properly. Set a short timeout on the next step so
-		// that we return faster.
-		ctx, cancel := context.WithTimeout(req.ctx, time.Second)
-		defer cancel()
-		req.ctx = ctx
+		// sync tokens are updated properly. Set a zero timeout on the next step so
+		// that we return immediately.
+		req.timeout = 0
 	}
 
 	// TODO: handle ignored users