PyCharm: Debug Django Forms clean() override

Question

I overrode clean() in a derived forms class:

def clean(self):
    self.user = None
    cleaned_data = super(LoginForm, self).clean()

    username = cleaned_data["user_id"].lower()

But the debugger isn't stopping on breakpoints that I set within the overridden method (e.g., it doesn't stop on a break set on self.user = None).

I can see that the method is being invoked because a custom ValidationError gets raised and recorded.

Is there a limitation on the PyCharm debugger where it won't hit breakpoints in overridden methods?