Unwanted QOpenGLWidget updates when docking a widget into same main window

We have a QMainWindow with QMDIArea as a central widget, and the MDI Area contains QOpenGLWidget subwindow. The QMainWindow has also a dock widget. Now, the QOpenGLWidget is unnecessarily repainted several times when the dock widget is docked or undocked. Also, an unnecessary repaint happens when the status bar of QMainWindow is updated.

These repaints don't happen if we use (obsolete) QGLWidget instead. And I was told this is not reproducible on OS X.

See the attached example. Simply dock and undock the dock widget (located at the bottom) and the debug output is flooded with the QOpenGLWidget::paintEvent() calls.