TypeError: Subscripted generics cannot be used with class and instance checks

Code:

    @wamp.register('network.xbr.console.find_markets', check_types=True)
    def find_markets(self,
                     created_from: Optional[int] = None,
                     limit: Optional[int] = None,
                     include_owners: Optional[List[bytes]] = None,
                     include_actors: Optional[List[bytes]] = None,
                     include_titles: Optional[List[str]] = None,
                     include_descriptions: Optional[List[str]] = None,
                     include_tags: Optional[List[str]] = None,
                     include_apis: Optional[List[bytes]] = None,
                     details: Optional[CallDetails] = None) -> List[bytes]:
        pass

Traceback:

2020-02-29T22:27:08+0100 [Router      26746] XbrNetworkApi.onUserError(): "TypeError: Subscripted generics cannot be used with class and instance checks"
Traceback (most recent call last):
  File "/home/oberstet/scm/crossbario/autobahn-python/autobahn/wamp/protocol.py", line 1020, in onMessage
    on_reply = txaio.as_future(endpoint.fn, *invoke_args, **invoke_kwargs)
  File "/home/oberstet/scm/crossbario/txaio/txaio/tx.py", line 365, in as_future
    return ensureDeferred(fun(*args, **kwargs))
  File "/home/oberstet/cpy381_5/lib/python3.8/site-packages/twisted/internet/defer.py", line 911, in ensureDeferred
    return _cancellableInlineCallbacks(coro)
  File "/home/oberstet/cpy381_5/lib/python3.8/site-packages/twisted/internet/defer.py", line 1529, in _cancellableInlineCallbacks
    _inlineCallbacks(None, g, status)
--- <exception caught here> ---
  File "/home/oberstet/cpy381_5/lib/python3.8/site-packages/twisted/internet/defer.py", line 1418, in _inlineCallbacks
    result = g.send(result)
  File "/home/oberstet/scm/crossbario/autobahn-python/autobahn/wamp/protocol.py", line 506, in _type_check
    if not isinstance(arguments[name], kind.__args__):
  File "/home/oberstet/cpy381/lib/python3.8/typing.py", line 766, in __instancecheck__
    return self.__subclasscheck__(type(obj))
  File "/home/oberstet/cpy381/lib/python3.8/typing.py", line 774, in __subclasscheck__
    raise TypeError("Subscripted generics cannot be used with"
builtins.TypeError: Subscripted generics cannot be used with class and instance checks

https://github.com/crossbario/xbr-www/blob/ad2a7c0e5659d1af22d8232b5682d2557a7e32c4/backend/xbrnetwork/_api.py#L1095

Start in autobahn/wamp/protocol.py at the _type_check call shown near line 506, then reproduce it with the check_types=True endpoint and annotations in xbrnetwork/_api.py near line 1095. Trace how Optional and List annotations are checked. Done means the endpoint no longer raises the reported TypeError while type checking its arguments.