Babel bluebirdCoroutine issue

compile.sh

# babel 5.8.23
babel --optional bluebirdCoroutines input.js > output.js

input.js

import Promise from 'bluebird';

export default class MyClass
{
  constructor() {
  }
  
  async foo() {
    var result = await Promise.delay('test', 500);
    
    console.log(result);
  }
}

output.js

'use strict';

var _bluebird = require('bluebird');

Object.defineProperty(exports, '__esModule', {
  value: true
});

var _createClass = (function () { function defineProperties(target, props) { for (var i = 0; i < props.length; i++) { var descriptor = props[i]; descriptor.enumerable = descriptor.enumerable || false; descriptor.configurable = true; if ('value' in descriptor) descriptor.writable = true; Object.defineProperty(target, descriptor.key, descriptor); } } return function (Constructor, protoProps, staticProps) { if (protoProps) defineProperties(Constructor.prototype, protoProps); if (staticProps) defineProperties(Constructor, staticProps); return Constructor; }; })();

function _interopRequireDefault(obj) { return obj && obj.__esModule ? obj : { 'default': obj }; }

function _classCallCheck(instance, Constructor) { if (!(instance instanceof Constructor)) { throw new TypeError('Cannot call a class as a function'); } }

var _bluebird2 = _interopRequireDefault(_bluebird);

var MyClass = (function () {
  function MyClass() {
    _classCallCheck(this, MyClass);
  }

  _createClass(MyClass, [{
    key: 'foo',
    value: _bluebird.coroutine(function* () {
      var result = yield _bluebird2['default'].delay('test', 500);

      console.log(result);
    })
  }]);

  return MyClass;
})();

exports['default'] = MyClass;
module.exports = exports['default'];