diff --git a/test/index.test.js b/test/index.test.js
index 08eb46a..989cda1 100644
--- a/test/index.test.js
+++ b/test/index.test.js
@@ -1,6 +1,7 @@
 'use strict';
 
 const assert = require('assert');
+const co = require('co');
 const mongoose = require('mongoose');
 const mongooseLeanVirtuals = require('../');