Unable to close a QMdiSubWindow with a QVideoWidget

If I put a QVideoWidget inside a QMdiSubWindow, the sub window can't be closed.

Simple code to reproduce the bug:

QMainWindow* mainWindow = new QMainWindow();
QMdiArea* mdiArea = new QMdiArea(mainWindow);
mainWindow->setCentralWidget(mdiArea);
QMdiSubWindow* subWindow = new QMdiSubWindow(mdiArea);
subWindow->setWidget(new QVideoWidget());
mdiArea->addSubWindow(subWindow);
subWindow->show();
mainWindow->show();

If I try to close the sub window by clicking the close button, the sub window stays open.

A workaround would be appreciated...

EDIT:

A QMdiSubWindow with a QVideoWidget inside prevents to close all other sub windows in the mdi area, even though they don't contain a QVideoWidget

If I add this code to the example above...

QMdiSubWindow* subWindow2 = new QMdiSubWindow(mdiArea);
mdiArea->addSubWindow(subWindow2);
subWindow2->show();

... I can't close both sub windows.

Also, even if I delete the subWindow with the QVideoWidget, I can't close any sub window added to the mdiArea (regardless it is added after or before the deletion)