Dragging file from Eclipse to DOpus not working

I just tried to drag and drop a file from my Eclipse IDE (Different versions) to a DOpus lister, but that doesn't seem to work. The process is basically stopped without any error, the file just doesn't land into the destination which the DOpus lister points to.

Dragging from Eclipse directly for example to the desktop works fine, but that means no DOpus lister is used.

Bug or just unsupported?