setting WA_NativeWindow attribute doesn't immediately create native window

#include <QtGui>

int main(int argc, char *argv[])
{
    QApplication app(argc, argv);
    QWidget w;
    w.setAttribute(Qt::WA_NativeWindow);
    w.setAttribute(Qt::WA_DontCreateNativeAncestors);
    w.createWinId();
    QWidget w2(&w);
    w2.setAttribute(Qt::WA_NativeWindow);
    w2.setAttribute(Qt::WA_DontCreateNativeAncestors);
    qDebug() << &w2 << w2.internalWinId();
    w.show();
    return app.exec();
}