Clicking on checkbox of a parent with children set state to Qt::PartiallyChecked instead of Qt::Checked

I attached a simple project that shows the issue:
There is a QTreeWidget with one top level item that has 10 children.
I do not set Qt::ItemIsTristate for the children, but with Qt5 when I click on the root item state of check box of the root item and its children changed to Qt::PartiallyChecked instead of Qt::Checked that is wrong.

P.S.: It works correctly with Qt-4