diff --git a/passthrough-proxy-with-keyvalidation/app.js b/passthrough-proxy-with-keyvalidation/app.js
index 8ec527e..6768719 100755
--- a/passthrough-proxy-with-keyvalidation/app.js
+++ b/passthrough-proxy-with-keyvalidation/app.js
@@ -16,7 +16,7 @@ a127.init(function(config) {
   app.use(function(err, req, res, next) {
     if (err && typeof err === 'object') {
       Object.defineProperty(err, 'message', { enumerable: true });
-      res.end(JSON.stringify(err));
+      return res.end(JSON.stringify(err));
     }
     next(err);
   });