Custom Error messages in Inlineformset does not work.

I created an inlineformset like so:

formset = forms.inlineformset_factory(
    Parent,
    Child,
    form=ChildForm,
    extra=1,
    min_num=2,
    max_num=5,
    can_delete=True,
    validate_min=True,
    validate_max=True,
    error_messages={'too_few_forms': 'Please provide more than one child'}
)

In the template, I still get the default error message when the User does not provide values for the formset or Child forms. What am I missing?