Popupmenu and advSmoothListBox

I want to use the popupmenu with a smooth listbox control. I try to attach a popumenu to the listboxItem, but when I set a value in DefaultItem.PopupMenu at design the setting goes to null at runtime.
When I set PopupMenu of the SmoothListBox at design it works. When I set lisboxItem.PopupMenu at runtime it works.

Same problem with DBAdvSmoothListBox.