Corner widget in QTabWidget doesn't show up

The corner widget in a QTabWidget doesn't render at all.
I have tried to use QToolButton and QLabel.

Code:

---

{
    QTabWidget tw;
    QLabel *label = new QLabel("foo");
    tw.setCornerWidget (label);
}

---

Simple enough, and I do see a little extra space at the beginning of the tab-list, but nothing is rendered there.

Try showing the label.

Well, it worked, after QLabel was parented to the tab! Usually these things are auto-parented; and that's why the confusion.

Code:

---

{
    QTabWidget tw;
    QLabel *label = new QLabel("foo", &tw);
    tw.setCornerWidget (label);
}

---