problem with QWebView, Plastique style and scroll bars on OSX

The following code produce a scroll bar with no handle on OSX

int main(int argc, char *argv[])
{
QApplication app(argc, argv);
QWebView wv;
wv.load(QUrl("http://www.tsr.ch"));
wv.setStyle(new QPlastiqueStyle());
wv.show();
return app.exec();
}