QGroupBox does not pass on focus to the correct widget

Consider the following:

A QGroupBox has three QRadioButtons inside a vertical layout. The second radio button is checked. When the QGroupBox is about to receive focus from tabbing, the first radio button is given focus.

However, the expected result is that the checked radio button is given focus.

If one of the radio buttons is checked by the user at run-time, focus will be given this radio button the next time the group box is about to receive focus.