Warning spew when reparenting native frameless window with translucent background onto another window

int main(int argc, char *argv[])
{
    QApplication a(argc, argv);

    QWidget* foo = new QWidget();
    foo->setWindowFlags(foo->windowFlags() | Qt::FramelessWindowHint);
    foo->setAttribute(Qt::WA_NativeWindow);
    foo->setAttribute(Qt::WA_TranslucentBackground);

    QWidget w;
    w.setLayout(new QVBoxLayout());
    w.layout()->addWidget(foo);
    w.show();
    return a.exec();
}