No restore button in QDockWidget title bar

Hi,
Since Qt 4.3, the restore button has dissapeared from the title bar of the dockwidgets when they are undocked, now only the close button is present. Do I have to activate it explicitly somehow? I tried with setFeatures and even setWindow flags but still doesn't work (it is there when the widget is docked though).
Any ideas?

Thanks!

170604 - Icon to restore widget missing from undocked QDockWidget:

Quote:

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Rejected:
Native floating dockwidgets do not have the button (see VS).

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