After hiding an application, when it is reshown sheets do not show content and are not connted to their parenting windows

#include <QtGui>

class Dialog : public QDialog
{
public:
  Dialog(QWidget *parent=0);
};

Dialog::Dialog(QWidget* parent) : QDialog(parent)
{
  setWindowModality(Qt::WindowModal);
#ifdef Q_OS_MAC
  setWindowFlags(Qt::Sheet);
#endif

   QGridLayout* grid = new QGridLayout(this);
   grid->addWidget(new QLabel("Content will disappear and sheet will disconnect from\nwindow when re shown after hiding the application"), 0,0);
}

int main(int argc, char **argv)
{
  QApplication app(argc, argv);

  QWidget w;
  Dialog* d = new Dialog(&w);
  d->show();
  w.show();

  return app.exec();
}