when running babel on `bar.js`, the output method `_interopRequireDefault` will have the return object with property `default` be unquoted. Commenting out line 6, will make `default` be quoted properly.

.babelrc

{
  "presets": [ "es3", ["es2015", {"loose": true}] ]
}

bar.js

import Foo from './foo';

class Bar {};

// commenting out this file causes the `interopRequireDefault` method to have an unquoted `default` property name 
typeof "foo";

foo.js

export default class Foo {};