The documentation specifically mentions returning an empty QVariant rather than returning 0 so I'd hope it wouldn't be that.

Running the same code but using a QTableView instead calls with role values of 6, 7, 9, 10, 1, 0 and 8. I reckon it might actually be something weird going on with the QListView. I wonder if maybe the Jambi implementation requires me to trigger something that the QTableView doesn't?

Thanks for your help with this. I think it might be worth seeing whether I can contact the Qt developers and logging a bug report or something. I've managed to find myself a work-around for now, it's not ideal but it's not too clunky and just avoids the QListView control.