QQuickWidget distorts focus handling

#include <QQuickWidget>
#include <QtWidgets>

class MainWindow : public QMainWindow {
    Q_OBJECT
public:
    MainWindow()
    {
        QAction *exitAction = new QAction(tr("Exit"), this);
        QAction *aboutQtAct = new QAction(tr("About Qt"), this);

        connect(exitAction, SIGNAL(triggered()), qApp, SLOT(quit()));
        connect(aboutQtAct, SIGNAL(triggered()), qApp, SLOT(aboutQt()));

        QMenu* fileMenu = menuBar()->addMenu(tr("File"));
        fileMenu->addAction(exitAction);

        QMenu* helpMenu = menuBar()->addMenu(tr("About"));
        helpMenu->addAction(aboutQtAct);
    }
};

int main(int argc, char **argv)
{
    QApplication app(argc, argv);
    QMainWindow *toplevel = new MainWindow;

    QUrl source("qrc:quickwidget/rotatingsquare.qml");
    QQuickWidget *w = new QQuickWidget;
    w->resize(300,300);
    w->setResizeMode(QQuickWidget::SizeRootObjectToView);
    w->setSource(source);

    toplevel->setCentralWidget(w);
    toplevel->show();
    return app.exec();
}

#include "main.moc"