promisfy lbrary function not found

I tried to use bluebird to promisfy couchbase's ottoman ODM library, but it does not work, with this error:

Cannot read property 'then' of undefined

couch.js:

import ottoman from 'ottoman'
import couchbase from 'couchbase';
import Promise from 'bluebird';

Promise.promisifyAll(ottoman);

const cluster = new couchbase.Cluster('couchbase://127.0.0.1');
const bucket = cluster.openBucket('transaction');
ottoman.store = new ottoman.CbStoreAdapter(bucket, ottoman);

export default ottoman;

message.js:

import ottoman from './couch';

const Message = ottoman.model('Message', {
    name: 'string'
});

export default Message;

index.js:

 import Message from './message';

 let message = new Message ({name:'Couch'});
    message.save().then((result) => {
        console.log(result);
    }).catch((err) => {
        console.log(err);
    })

via Alvin