QToolButton popup menu is shown at wrong position when embedded in a QGraphicsView

#include <QtGui>

class widget : public QGraphicsView
{
public:
    widget(QWidget* parent = 0)
        : QGraphicsView(parent)
    {
        QGraphicsScene* scene = new QGraphicsScene(0, 0, 6000, 6000, this);
        setScene(scene);

        QToolButton* tb = new QToolButton;
        tb->setText("...");
        QMenu* menu = new QMenu("&File");
        menu->addAction("hello");
        tb->setPopupMode(QToolButton::MenuButtonPopup);
        tb->setMenu(menu);

        QGraphicsProxyWidget* proxy = scene->addWidget(tb);
        tb->move(5900, 10);
        tb->show();
    }
};

int main(int argc, char **argv)
{
    QApplication a(argc, argv);
    widget w;
    w.show();
    return a.exec();
}

#include <QtGui> 

class widget : public QGraphicsView 
{ 
public: 
widget(QWidget* parent = 0) 
: QGraphicsView(parent) 
{ 
QGraphicsScene* scene = new QGraphicsScene(); 
setScene(scene); 

QMenu * menu = new QMenu(); 
menu->addAction( "foo" ); 

QPushButton * button = new QPushButton( "Push Me" ); 
button->setMenu( menu ); 

QGraphicsProxyWidget* proxy = scene->addWidget(button); 
button->show(); 
} 
}; 

int main(int argc, char **argv) 
{ 
QApplication a(argc, argv); 
widget w; 
w.show(); 
return a.exec(); 
}