QComboBox font settings does not work when Fusion style is used

#include "mainwindow.h"
#include <QApplication>
#include <QComboBox>
#include <QProxyStyle>
#include <QPainter>

int main(int argc, char *argv[])
{
    QApplication a(argc, argv);
    QComboBox box;
    box.addItems(QStringList() << "one" << "two" << "three");
    QFont font;
    font.setBold(true);
    font.setItalic(true);
    font.setPixelSize(20);
    box.setItemData(0, font, Qt::FontRole);
    box.show();

    return a.exec();
}