wasp build start

Feels really stupid to ask this but i can't manage to get

wasp build start

wasp build start

running.
I always get the message, that the DATABASE_URL is not defined (from the prisma file).
But i run

DATABASE_URL=<url> wasp build

DATABASE_URL=<url> wasp build

and even if i run

DATABASE_URL=<url> wasp build start

DATABASE_URL=<url> wasp build start

afterwards i get the exact same error.
What am I missing?

wasp build start - Wasp