Adding a stage package like this one: stage-packages: ['hello:invalid'] results in the following suggestion: You may need to add support for this architecture with 'dpkg --add-architecture invalid'. If you actually go ahead an run that command, dpkg will not complain about the invalid architecture, which leaves you with invalid apt sources. You won't be able to run apt update, and thus you won't be able to run snapcraft. I think we should only suggest to add the architecture if it is a valid one.