QMimeData: hasUrls returns true but urls() is empty

[Violet Giraffe]

I have my QStandardItemModel descendant with mimeData() implemented. It works great for drag and drop. But oddly enough, when I do

@ QApplication::clipBoard()->setMimeData(_model->mimeData(...)) @

and then

@_model->dropMimeData(QApplication::clipBoard()->mimeData(), Qt::CopyAction, 0, 0, QModelIndex());@

the QMimeData object returns true for hasUrls(), but urls() is empty. What's the problem?
This is on Windows.

[Violet Giraffe]

Ideas anyone?