Ribbon PopupButton closing during DragDrop

I have a Ribbon PopupButton whose content is a DockPanel containing a ListBox and several other controls. When I call:

DragDropEffects effects = DragDrop.DoDragDrop(listbox, d, DragDropEffects.Copy | DragDropEffects.Move);

The popup closes and the DragDropEffects come back None.

I would really like to be able to sandwich the DoDragDrop like this:

myPopupBtn.CanClose == false;
DragDropEffects effects = DragDrop.DoDragDrop(listbox, d, DragDropEffects.Copy | DragDropEffects.Move);
myPopupBtn.CanClose == true;

Is there any current solution to my problem?