SortFilterModel cannot sort by a numeric role

This is invalid. For future reference, the situation is slightly more complex. I’m trying to do something like that:

  SortFilterModel {
    sort.property: "blah"
    sort.order: Qt.DescendingOrder
    model: CustomSortFilterModel {
      sourceModel: CustomListModel {}
    }
  }

where CustomListModel is a custom QAbstractListModel and CustomSortFilterModel is a custom QSortFilterProxyModel that does sorting and filtering. When model gets set on the SortFilterModel, its sourceModel might not have been set yet, so querying the roleNames will return an empty QHash, and subsequent attempts to sort the model will fail because property "blah" couldn’t be matched to a role index.

And it appears that if I instantiate the models at the same level, without nesting them, this works:

  CustomListModel { id: customListModel }
  CustomSortFilterModel { id: customSortFilterModel }
  SortFilterModel {
    sort.property: "blah"
    sort.order: Qt.DescendingOrder
    model: customSortFilterModel
  }