Regression: context menu with submenu crashes on second open

#include <QApplication>
#include <QContextMenuEvent>
#include <QMainWindow>
#include <QMenu>

class MainWindow : public QMainWindow
{
public:
  MainWindow(QWidget *parent = 0)
    : QMainWindow(parent)
  {
    submenu = new QMenu("Submenu", this);
  }

  virtual void contextMenuEvent(QContextMenuEvent *event)
  {
    submenu->clear();
    QAction *action = submenu->addAction("Test");
    action->setData(0); // Crash happens here second time...

    QMenu menu;
    menu.addMenu(submenu);
    menu.exec(event->globalPos());
  }

private:
  QMenu *submenu;
};

int main (int argc, char *argv[])
{
  QApplication app(argc, argv);
  MainWindow window;
  window.show();
  return app.exec();
}