DefaultWorkItem does not allow group in Assigned To

I've created a new process template with TFS Power Tools. I added a group [project]\Developers. I changed the type definition of the Task-type so that "Assigned To" has 2 rules now:

1. ALLOWEXISTINGVALUE


2. ALLOWEDVALUES ([project]\Developers in list)

Now when I create a default work item and open the Assign To combo, it shows me "$$PROJECTNAME$$\Developers. If I select this, upload the template and try to create a team project the assistent comes up with the following error:

TF26214: Cannot save the work item. Fields with errors: Assigned To

TF237086: The work item cannot be saved because at least one field contains a value that is not allowed.

If I remove the default work item the team project is created successfully and I can add a new work item by hand using the Developers-group in Assinged To.

---