Missing _has_changed on widget

Django version: 1.6.5
Dojango version: git 2fc8c88

I get the following backtrace when using a formset:

[...]

File "d:\mysite\django\forms\formsets.py", line 292, in is_valid
err = self.errors

File "d:\mysite\dojango\forms\formsets.py", line 56, in getattribute
return super(BaseFormSet, self).getattribute(anatt)

File "d:\mysite\django\forms\formsets.py", line 267, in errors
self.full_clean()

File "d:\mysite\django\forms\formsets.py", line 315, in full_clean
self._errors.append(form.errors)

File "d:\mysite\django\forms\forms.py", line 121, in errors
self.full_clean()

File "d:\mysite\django\forms\forms.py", line 271, in full_clean
if self.empty_permitted and not self.has_changed():

File "d:\mysite\django\forms\forms.py", line 324, in has_changed
return bool(self.changed_data)

File "d:\mysite\django\forms\forms.py", line 357, in changed_data
if field.widget._has_changed(initial_value, data_value):

File "d:\mysite\dojango\forms\widgets.py", line 243, in _has_changed
return super(TimeInput, self)._has_changed(self._format_value(initial), data)

AttributeError: 'super' object has no attribute '_has_changed'