webhook res: undefined

I try use your awesome framework to build a simple test on heroku and I received this error on deploy:
```
webhook res: undefined
```

index.js
```
var bb = require('bot-brother')

var bot = module.exports = bb({
    key: process.env.TOKEN,
    webHook: {
        url: process.env.HEROKU_URL,
        port: 8443,
        https: false
    }
})
```
Have you any suggestion? Thank you!