on_touch_up getting called twice due to grab

uptouch.py

from kivy.properties import NumericProperty
from kivy.uix.widget import Widget
from kivy.logger import Logger
from kivy.app import App


class TouchUpListener(Widget):
    n = NumericProperty(0)

    def on_touch_down(self, touch):
        touch.grab(self)

    def on_touch_up(self, touch):
        Logger.info("TouchUpListener: on_touch_up #{}".format(self.n))
        self.n += 1


class TouchUpTestApp(App):
    def build(self):
        return TouchUpListener()


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