QFont(family) and QFont::setFamily() give different results

#include <QtGui>

int main(int argc, char *argv[])
{
    QApplication app(argc, argv);

    QFont f1("Times");
    qDebug() << f1.family() << " xHeight: " << QFontMetrics(f1).xHeight();
    // "Times"  xHeight:  4 

    QFont f2;
    f2.setFamily("Times");
    qDebug() << f2.family() << " xHeight: " << QFontMetrics(f2).xHeight();
    // "Times"  xHeight:  3

    return 0;
}