QMainWindow: Context menu for central widget is not available - MAC OS X

When bringing up the context menu on a central widget in QMainWindow on Mac and then clicking outside the application, the context menu is closed and the application looses focus as expected. However, clicking on the application again the context menu is no longer possible to bring up. One needs to either click outside the application again or bring up the context menu for one of the dockwidgets.
This can be reproduced with the mainwindow demo in Qt.