DataObject from canvas is missing in assignments when case file var is present

Create Case definition in Case project. Add Case File variable to the process. Create DataObject on canvas. Create node with assignments (e.g. User task) on canvas or in sub-process. Activate node with assignments, open assignments and click on Source/Target. Actual result DataObject is missing in listed items. Expected result Both Case file variable as well as DataObject from Canvas is present in listed items.