custom event binding order issue

main.py

#!/usr/bin/python3


from kivy.app import App
from kivy.uix.boxlayout import BoxLayout
from kivy.uix.button import Button


class AfterSuperButton(Button):
    def __init__(self, **kwargs):
        super(AfterSuperButton, self).__init__(**kwargs)
        self.register_event_type('on_custom')

    def on_custom(self, *args):
        self.text += ' - buttons on custom hit - '


class BeforeSuperButton(Button):
    def __init__(self, **kwargs):
        self.register_event_type('on_custom')
        super(BeforeSuperButton, self).__init__(**kwargs)

    def on_custom(self, *args):
        self.text += ' - buttons on custom hit - '


class NoPostBindBox(BoxLayout):
    def __init__(self, **kwargs):
        super(NoPostBindBox, self).__init__(**kwargs)
        self.add_widget(BeforeSuperButton(text='before, no post bind', on_custom=self.update_text))
        self.add_widget(AfterSuperButton(text='after, no post bind', on_custom=self.update_text))

    def update_text(self, button):
        print('update_text NoPostBindBox')
        button.text += 'changed from NoPostBindBox'


class PostBindBox(BoxLayout):
    def __init__(self, **kwargs):
        super(PostBindBox, self).__init__(**kwargs)
        before = BeforeSuperButton(text='before, with post bind')
        before.bind(on_custom=self.update_text)
        after = AfterSuperButton(text='after, with post bind')
        after.bind(on_custom=self.update_text)
        self.add_widget(before)
        self.add_widget(after)

    def update_text(self, button):
        print('update_text PostBindBox')
        button.text += 'changed from BindBox'


class SuperApp(App):
    pass

if __name__ == '__main__':
    SuperApp().run()

super.kv

<AfterSuperButton>:
    text: 'AfterSuperButton'
    on_release: self.dispatch('on_custom')

<BeforeSuperButton>:
    text: 'BeforeSuperButton'
    on_release: self.dispatch('on_custom')

GridLayout:
    cols: 1
    NoPostBindBox:
    PostBindBox: