Invalid workflow action with 'Assignee only' condition and AssignTo field on transition screen

We just upgraded from 3.3 to 3.6 and no my workflow stops working.

Whenever a workflow transition has the 'Assignee only' condition set and the screen used for the workflow transition allows setting the AssignTo field, the transition will fail (see screenshot)

Steps to reproduce the issue at will:

• copy the default jira worklow
• in this copied workflow change the 'Start Progress' step to use the 'Resolve Issue Screen'. This step already has the 'Assignee only' condition and the 'Resolve Issue Screen' has the AssignTo field.
• Create a new workflow scheme
• Assignt the copied workflow to All Unassigned Issue Types in this new workflow scheme
• Edit a project to use this new workflow scheme
• Logon as a jira-developer
• Create a new issue in this project
• Assign the issue to yourself
• Select the 'Start Progress' workflow action
• Set the AssignTo field to another user than yourself
• Click the StartProgress button
• The following error will apear: "Errors: Action 4 is invalid"