this inside an async object method

I creating an object that uses async function methods with babel-polyfill/babel-preset-es2017, however I am having a problem with this:

let obj = () => {
    return {
        doAsync: async () => {
            let thing = await longProcess()
            return this.transform(thing)
        },

        transform: (thing) => {
            return psuedoCodeTransform(thing)
        }
    }
}

let instance = obj()
instance.doAsync()
// TypeError: cannot read property 'transform' of undefined`.

Is this something described in ES2017, a babel-polyfill/regeneratorRuntime gotcha?