QTableWidget displays widgets in its cells incorrectly

#include <QApplication>
#include <QTableWidget>
#include <QPushButton>
#include <QHeaderView>

int main(int argc, char *argv[])
{
    QApplication a(argc, argv);
    QTableWidget table(5, 5);
    for (int i = 0; i < 5; ++i)
    {
        for (int j = 0; j < 5; ++j)
            table.setCellWidget(i, j, new QPushButton("0", &table));
    }

    table.horizontalHeader()->setDefaultSectionSize(40);
    table.resize(300, 200);
    table.show();

    return a.exec();
}