diff --git a/polyfill/XMLHttpRequest.js b/polyfill/XMLHttpRequest.js
index 42c987704..e889637c8 100644
--- a/polyfill/XMLHttpRequest.js
+++ b/polyfill/XMLHttpRequest.js
@@ -358,6 +358,7 @@ export default class XMLHttpRequest extends XMLHttpRequestEventTarget{
         case 'json':
           this._response = resp.json()
           this._responseText = resp.text()
+          responseDataReady();
         break
         default :
           this._responseText = resp.text()