Mac Accessibility: QComboBox drop down list is not read out with Voice Over keyboard

With Voice over keyboard, selected item of combobox drop down list is not being spoken.
Attached example reproduces this, Steps to reproduce:
1. Extract, build and run the attached simple Qt app in Qt Creator.
2. Enable Voice Over (System Preferences > Accessibility > Voice Over > Enable Voice Over).
3. Return the focus to the Qt app.
4. Move the black focus ring onto the combo box.
5. Type the Voice Over shortcut to open the combo box: Ctrl+Option+Space.

EXPECTED: The combo box opens, and Voice Over reads the text of the selected item.
ACTUAL:
With Qt5.2:
The combo box does not open though Voice Over reports that the combo box has been "pressed".
With Qt5.3:
After Ctrl+Option+Space. Combo Box does opens but it doesn't say anything: if you then hit down arrow, the first time it says 'FullScreenTest has a new window, but it doesn't read the contents of the selected item in the pop-up.