Ошибка при запуске kivy-examples

ubutu, python 3.8 Ошибка:

Traceback (most recent call last):
   File "main.py", line 192, in <module>
     KivyCatalogApp().run()
   File "/usr/lib/python3/dist-packages/kivy/app.py", line 826, in run
     runTouchApp()
   File "/usr/lib/python3/dist-packages/kivy/base.py", line 502, in runTouchApp
     EventLoop.window.mainloop()
   File "/usr/lib/python3/dist-packages/kivy/core/window/window_sdl2.py", line 727, in mainloop
     self._mainloop()
   File "/usr/lib/python3/dist-packages/kivy/core/window/window_sdl2.py", line 460, in _mainloop
     EventLoop.idle()
   File "/usr/lib/python3/dist-packages/kivy/base.py", line 346, in idle
     Clock.tick_draw()
   File "/usr/lib/python3/dist-packages/kivy/clock.py", line 588, in tick_draw
     self._process_events_before_frame()
   File "kivy/_clock.pyx", line 427, in kivy._clock.CyClockBase._process_events_before_frame
   File "kivy/_clock.pyx", line 467, in kivy._clock.CyClockBase._process_events_before_frame
   File "kivy/_clock.pyx", line 465, in kivy._clock.CyClockBase._process_events_before_frame
   File "kivy/_clock.pyx", line 154, in kivy._clock.ClockEvent.tick
   File "kivy/_clock.pyx", line 86, in kivy._clock.ClockEvent.get_callback
   File "/usr/lib/python3/dist-packages/kivy/weakmethod.py", line 56, in is_dead
     return self.proxy is not None and not bool(dir(self.proxy))
 ReferenceError: weakly-referenced object no longer exists