Assebly definition dependent on asset store package without assembly definition

I'm planning to make a unity package which is dependent on an asset store package. This means i will need an assembly definition for my package which is dependent on the asset store package. Unfortunately, the asset store package does not use assembly definitions, so i cannot make my assembly definition dependent on it. How do i handle this?

An obvious solution would be to just add an assembly definition to the asset store package after importing it, but then any users of my package would have to do the same and make sure that the settings of that assembly definition is correct. That would work, but it doesn't seem like a particularly clean way of doing things.

Is there a better way?