Inconsistency of ampersand handling in window title of docked and undocked widgets

I'm want to display '&' in docked widget's title. However, I can't do that because of its inconsistent handling.
When it's docked, I have to use "&&" to display a single "&". However, once I undock it (under Windows), I see "&&" displayed in its title.

It's better under Linux since even when undocked, the window contains its own title bar with a single "&". However, if I enable window manager title on that window, the window manager title displays "&&".

I guess what should be done is that the widget's window manager title should be cleared of extra ampersands when undocking, while its real title should remain the same (so that accelerators can still be used).

I'm attaching a sample .ui file that shows the behavior. Open it in Qt Designer, press ctrl-R and dock / undock the dock widget to observe the bug.