diff --git a/.travis.yml b/.travis.yml
index 919df57d..01531754 100644
--- a/.travis.yml
+++ b/.travis.yml
@@ -1,7 +1,7 @@
 language: node_js
 node_js:
-  - "4.4"
-  - "6.3"
+  - "4.5"
+  - "6.6"
 services:
   - mongodb
 cache:
diff --git a/index.js b/index.js
index 8b434bb8..96fd9195 100644
--- a/index.js
+++ b/index.js
@@ -3,8 +3,8 @@ import mongoose from 'mongoose';
 import config from './config/env';
 import app from './config/express';
 
-// promisify mongoose
-Promise.promisifyAll(mongoose);
+// plugin bluebird promise in mongoose
+mongoose.Promise = Promise;
 
 // connect to mongo db
 mongoose.connect(config.db, { server: { socketOptions: { keepAlive: 1 } } });
diff --git a/server/controllers/user.js b/server/controllers/user.js
index 96ac952e..d80c39b5 100644
--- a/server/controllers/user.js
+++ b/server/controllers/user.js
@@ -4,10 +4,12 @@ import User from '../models/user';
  * Load user and append to req.
  */
 function load(req, res, next, id) {
-  User.get(id).then((user) => {
-    req.user = user;		// eslint-disable-line no-param-reassign
-    return next();
-  }).error((e) => next(e));
+  User.get(id)
+    .then((user) => {
+      req.user = user;		// eslint-disable-line no-param-reassign
+      return next();
+    })
+    .catch((e) => next(e));
 }
 
 /**
@@ -30,9 +32,9 @@ function create(req, res, next) {
     mobileNumber: req.body.mobileNumber
   });
 
-  user.saveAsync()
+  user.save()
     .then((savedUser) => res.json(savedUser))
-    .error((e) => next(e));
+    .catch((e) => next(e));
 }
 
 /**
@@ -46,9 +48,9 @@ function update(req, res, next) {
   user.username = req.body.username;
   user.mobileNumber = req.body.mobileNumber;
 
-  user.saveAsync()
+  user.save()
     .then((savedUser) => res.json(savedUser))
-    .error((e) => next(e));
+    .catch((e) => next(e));
 }
 
 /**
@@ -59,8 +61,9 @@ function update(req, res, next) {
  */
 function list(req, res, next) {
   const { limit = 50, skip = 0 } = req.query;
-  User.list({ limit, skip }).then((users) =>	res.json(users))
-    .error((e) => next(e));
+  User.list({ limit, skip })
+    .then((users) =>	res.json(users))
+    .catch((e) => next(e));
 }
 
 /**
@@ -69,9 +72,9 @@ function list(req, res, next) {
  */
 function remove(req, res, next) {
   const user = req.user;
-  user.removeAsync()
+  user.remove()
     .then((deletedUser) => res.json(deletedUser))
-    .error((e) => next(e));
+    .catch((e) => next(e));
 }
 
 export default { load, get, create, update, list, remove };
diff --git a/server/models/user.js b/server/models/user.js
index ed96abd2..650035cb 100644
--- a/server/models/user.js
+++ b/server/models/user.js
@@ -46,7 +46,8 @@ UserSchema.statics = {
    */
   get(id) {
     return this.findById(id)
-      .execAsync().then((user) => {
+      .exec()
+      .then((user) => {
         if (user) {
           return user;
         }
@@ -66,7 +67,7 @@ UserSchema.statics = {
       .sort({ createdAt: -1 })
       .skip(skip)
       .limit(limit)
-      .execAsync();
+      .exec();
   }
 };