Esc key doesn't cancel drag and drop operation until mouse button release occurs

#include <QtGui>

class TreeWidget : public QTreeWidget
{
    Q_OBJECT
public:
    TreeWidget() : QTreeWidget(0)
    {
        setAcceptDrops(true);
        setDragEnabled(true);
        new QTreeWidgetItem(this, QStringList() << "Oak");
        new QTreeWidgetItem(this, QStringList() << "Fir");
        new QTreeWidgetItem(this, QStringList() << "Pine");
    }
};

#include "main.moc"

int main(int argc, char **argv)
{
    QApplication app(argc, argv);
    QWidget widget;
    TreeWidget box;
    QVBoxLayout layout(&widget);
    layout.addWidget(&box);
    widget.show();
    return app.exec();
}