Anyone an idea why this code segfaults?

[Kumosan]

The general problem is that you try to modify an object which is passed as an argument of a signal and if there are more than one slots connected to that signal, the second (and consecutive) slots may be called for invalid data. That's why you should avoid situations where you delete the signal argument from inside a slot. You can overcome the problem by moving the deletion to after all slots have been fired (for example use a single shot timer with 0 timeout that will perform the actual delete).

Nope, this is not the problem. No passed object to a slot. In a context menu event a QAction is created, which calls a method 'deleteSelected()'. deleteSelected() has a pointer to the model, fetches the selected indices from that model and starts to delete. No signal/slot or passed parameter involved at all.

I think the QPersistentModel hint was the right idea.

QPersistenModel was definitely the right idea. Problem solved.