Can't start stack with timescaledb checked: services.timescaledb.environment contains an invalid type, it should be an object, or an array

[KlausHans]

If i try to start (aka docker compose) my stack with timescaledb checked i get this error:

ERROR: The Compose file './docker-compose.yml' is invalid because:
services.timescaledb.environment contains an invalid type, it should be an object, or an array

In the yaml file the environment of timescale is specified as

environment: POSTGRES_USER=timescaleuser POSTGRES_PASSWORD=%randomPassword% POSTGRES_DB=postdb

This is obviously wrong syntax. If i change it by hand to

    environment:
    - POSTGRES_USER=timescaleuser
    - POSTGRES_PASSWORD=%randomPassword%
    - POSTGRES_DB=postdb

docker compose works.