flask_pymongo can't access mongodb with auth

Question

I use Flask and Flask-Pymongo

from flask_pymongo import PyMongo
user = PyMongo(app, uri='mongodb://username:[email protected]:27018/user')

pymongo.errors.OperationFailure: Authentication failed.

But using Pymongo with same mongodb uri then work.

import pymongo
db = pymongo.MongoClient('mongodb://username:[email protected]:27018')