QKeySequence::toString(NativeText) returns empty string for Qt::KeypadModifier

#include <QApplication>
#include <QMessageBox>
int main(int argc, char *argv[])
{
  QApplication a(argc, argv);
  QMessageBox::information( 0, "",
    QKeySequence(Qt::KeypadModifier).toString(QKeySequence::NativeText) );
  return a.exec();
}

if ((key & Qt::KeypadModifier) == Qt::KeypadModifier)
  addKey(s, nativeText ? QCoreApplication::translate("QShortcut", "Numpad") : QString::fromLatin1("Numpad"), format);