QWizardPage: QComboBox as first widget in wizard page does not have focus rectangle

If a QComboBox is the first widget in a wizard page, it is not drawn with a focus rectangle when the page is shown. It does have focus (pressing space will open its popup), but there is no visual indication that it has this.

If a QPushButton is the first widget on the wizard page, however, the focus rectangle is drawn for the push button when the page is shown.