Mac: Menubar items disappears when opening a dockwidget with a mainwindow inside

On Mac the menubar items for the application disappears when opening a dockwidget where the widget inside the dockwidget is a QMainWindow.

The menubar items for the application disappears when the dockwidget is opened, and the menubar items do not return when the dockwidget is closed.

The menubar items in the dockwidget's QMainWindow is placed at the top of the window, similar as when QMAC_QMENUBAR_NO_MERGE is defined
for a QMainWindow.

The expected behaviour would be to have the menubar items for the top QMainWindow reappear when the dockwidget is closed. And possibly have the dockwidget with the QMainWindow place it's menubar items in the main mac menu.