new process definitions cannot be created in "empty" projects

I have an "empty" eclipse project with a custom ant script for building and deploying .par files. I can edit the contained process definitions in eclipse but I cannot create new processes. When I try to, I get "Source folder is not valid" message. The only workaround I've found is to create the process definition in another project (eg. an ejb jar) and then move the process to the correct project.

In my opinion, there is no reason to restrict creating process definitions to some type of projects only.