QPushButton with Qt::WA_MacSmallSize has incorrect focus frame

#include <QWidget>
#include <QPushButton>
#include <QVBoxLayout>
#include <QApplication>

int main(int argc, char *argv[])
{
    QApplication a(argc, argv);
    QWidget w;
    w.setLayout(new QVBoxLayout);

    QPushButton *b = new QPushButton("Normal");
    w.layout()->addWidget(b);

    b = new QPushButton("Small");
    b->setAttribute(Qt::WA_MacSmallSize);
    w.layout()->addWidget(b);

    b = new QPushButton("Mini");
    b->setAttribute(Qt::WA_MacMiniSize);
    w.layout()->addWidget(b);

    w.show();
    return a.exec();
}