Issues with quoting of Environment Variables

[roock]

I've run into the following issue when using the given examples:

Fatal: parsing repository location failed: invalid backend
If the repo is in a local directory, you need to add a `local:` prefix

The problem seems to be the false quoting of the RESTIC_REPOSITORY environment variable:

environment:
  - RESTIC_REPOSITORY="b2:bucket:some/path"

For me the following version is working:

environment: 
  - "RESTIC_REPOSITORY=b2:bucket:some/path"

update: the same issue also applied to the CRON_*_EXPRESSION environment variables

my setup:
Docker version 18.09.0-ce, build 4d60db472b
docker-compose version 1.23.2, build unknown

I didn't find anything about quoting in the docker compose documentation, but I've found the following stackoverflow question:

https://stackoverflow.com/questions/41988809/docker-compose-how-to-escape-environment-variables