diff --git a/tutorial/nodejs/NodeClientPromise.js b/tutorial/nodejs/NodeClientPromise.js
index fac12ba..2cdc184 100644
--- a/tutorial/nodejs/NodeClientPromise.js
+++ b/tutorial/nodejs/NodeClientPromise.js
@@ -20,7 +20,7 @@
 var thrift = require('thrift');
 var Calculator = require('./gen-nodejs/Calculator');
 var ttypes = require('./gen-nodejs/tutorial_types');
-
+const assert = require('assert');
 
 var transport = thrift.TBufferedTransport;
 var protocol = thrift.TBinaryProtocol;