Daphne/Twisted exception when serving SSL/TLS

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I get the following traceback shortly after running Daphne with TLS enabled (it doesn't occur when TLS is not configured). Any ideas? It doesn't seem to affect anything, but I thought I would bring it up here before trying to submit an issue:

2019-05-03 12:41:45,252 ERROR    Exception in callback AsyncioSelectorReactor.callLater.<locals>.run() at c:\users\user\virtualenvs\channels_test\lib\site-packages\twisted\internet\asyncioreactor.py:287

handle: <TimerHandle when=56886.125 AsyncioSelectorReactor.callLater.<locals>.run() at c:\users\user\virtualenvs\channels_test\lib\site-packages\twisted\internet\asyncioreactor.py:287>

Traceback (most recent call last):

  File "C:\Program Files\Python37\lib\asyncio\events.py", line 88, in _run

    self._context.run(self._callback, *self._args)

  File "c:\users\user\virtualenvs\channels_test\lib\site-packages\twisted\internet\asyncioreactor.py", line 290, in run

    f(*args, **kwargs)

  File "c:\users\user\virtualenvs\channels_test\lib\site-packages\twisted\web\http.py", line 2339, in forceAbortClient

    self.transport.abortConnection()

  File "c:\users\user\virtualenvs\channels_test\lib\site-packages\twisted\protocols\tls.py", line 435, in abortConnection

    self._shutdownTLS()

  File "c:\users\user\virtualenvs\channels_test\lib\site-packages\twisted\protocols\tls.py", line 338, in _shutdownTLS

    shutdownSuccess = self._tlsConnection.shutdown()

AttributeError: 'NoneType' object has no attribute 'shutdown'

This is on Windows 10, but I saw it on my Ubuntu server as well (again, when TLS is enabled).