showMinimize() won't work with Frameless main window

I have a QMainWindow with those 3 hints:

Qt::FramelessWindowHint | Qt::WindowMinimizeButtonHint | Qt::WindowSystemMenuHint

If I try to minimize the window with "showMinimized()" the widget will stay visible, in the same position. The only thing that will changes is that the window stops receiving input events until I click on it a few times.

There are no eventFilters nor anything else that might be causing this behavior.
Also, showMaximized() works as expected.