QComboBox and checkable QStandardItem

Hi,
I wrote a piece of code that filled a comboBox with checkable items (the project is joined).
With the windowsvista style, the behaviour is normal but with the Fusion style,
the items are not checkable/clickable and the checkbox are not rendered.
The QStandardItemModel::itemChanged signal is not emitted either.
I don't know if it is a bug or a normal behaviour.
A test on linux gives the same result.
In the latter case, is there any way to have checkable items ?
Sincerely.
Romain.