Redis – "Error: Configuration property is not defined" on `heroku local web` – Config / Heroku

I am trying to setup locally an existing Heroku app. To do so, I git cloned the app from our repo in Github. Then I added the git remote for heroku.

Normally, builds to the server happen with Travis CI, but now I want to run the app locally straight from heroku.

heroku config returns the config variables just fine.

But heroku local web returns the error

throw new Error(‘Configuration property "’ + property + ‘" is not defined’);

Error: Configuration property "redis.url" is not defined

redis.js

import config from 'config';
const redis = new Redis(config.get('redis.url'), {
  keyPrefix: 'kw:',
});

The config folder is in the root of my repo.

config/default.js

import dotenv from 'dotenv';

dotenv.config({ silent: true });

module.exports = {
  ...,
  redis: {
    url: process.env.REDIS_URL || process.env.REDISCLOUD_URL,
  },
  ...
}

Relevant scripts in package.js

    "start:server": "./node_modules/.bin/babel-node src/server.js",
    "start:worker": "./node_modules/.bin/babel-node src/worker/worker.js",
    "start": "./node_modules/.bin/nf start",

If I run npm run start:server I get the same error.

If I comment out the redis.url code I get the same error but for another variable in the config.

What am I missing? Let me know if you require clarification.