Symfony version(s) affected: 4.2.1

Description
I'm following the new approach to .env files as described here.

My .env file contains:

APP_ENV=dev
APP_DEBUG=1
STRIPE_KEY=

And my .env.local file contains:

STRIPE_KEY=MY_KEY

When I create a service that injects this %env(STRIPE_KEY)% it's always empty.

When I remove the STRIPE_KEY= placeholder from my .env file it suddenly works.

The issue is that it first loads the .env file, sets the STRIPE_KEY to blank, then loads the .env.local file and just skips the STRIPE_KEY=MY_KEY because it's already defined.

Possible Solution
Always let .env.local override the environment variables defined in .env