How can I set ember-simple-google-maps env variables?

Trying to configure settings for ember-simple-google-maps.

let ENV = {
  modulePrefix: 'app-name',
  environment,
  rootURL: '/',
  locationType: 'auto',
  EmberENV: {
    FEATURES: {},
    EXTEND_PROTOTYPES: {
      Date: false
    }
  },

  APP: {},

  firebase: {
    apiKey: "xxxxxx"
  },

  GOOGLE_MAPS_VERSION: '3.34',
  GOOGLE_MAPS_API_KEY: 'xxxxxxxxxx'
};

According to the documentation I should be able to set these variable but it doesn't work. Version isn't set to the latest and the API is not found. Any thoughts? I'm sure I'm missing something super obvious...

Aspects of the Google Maps Installation can be customized, by supplying environment variables to the server process.