QCombobox calculates container height wrong when using spacing

#include <QApplication>
#include <QComboBox>
#include <QListView>

int main(int argc, char *argv[])
{
    QApplication a(argc, argv);
    QComboBox* cb = new QComboBox();
    (qobject_cast<QListView*>(cb->view()))->setSpacing(4);
    int numOfItems=5;
    for(int i=0;i<numOfItems;i++)
        cb->addItem("item " + QString::number(i+1));
    cb->show();
    return a.exec();
}