QFont::setStretch ignored after calling QFont::setStyleName

QFont::setStretch is ignored and has no effect following any call to QFont::setStyleString.

Eg..

  QLabel *l = new QLabel();
  QFont f;
  f.setFamily( "Serif" );
  f.setStyleName( "Bold" );
  f.setStretch( 400 );
  l->setFont( f );
  l->setText( "test" );
  l->show();

Will ignore the stretch setting, while commenting out the "setStyleName" call will correctly show the stretched text.