diff --git a/lib/persistence/mongo.js b/lib/persistence/mongo.js
index 1bbc0c2..183ed18 100644
--- a/lib/persistence/mongo.js
+++ b/lib/persistence/mongo.js
@@ -26,8 +26,6 @@ OTHER DEALINGS IN THE SOFTWARE.
 
 var AbstractPersistence = require("./abstract");
 var escape = require('escape-string-regexp');
-var mongo = require('mongodb');
-var MongoClient = mongo.MongoClient;
 var util = require("util");
 var steed = require("steed")();
 var Matcher = require("./matcher");
@@ -167,6 +165,8 @@ function MongoPersistence(options, done) {
   if (options.connection) {
     connected(null, this.options.connection);
   } else {
+    var mongo = require('mongodb');
+    var MongoClient = mongo.MongoClient;
     MongoClient.connect(this.options.url, this.options.mongo, connected);
   }
 }