AssertionError: Popped wrong request context

[MarSoft]

Just tried testing this extension and bumped to this problem. Code is slightly modified "Hello World" variant:

from flask import Flask
from flask.ext.aiohttp import AioHTTP, async
from asyncio import sleep

app = Flask(__name__)
aio = AioHTTP(app)

@app.route('/')
@async
def index():
    yield from sleep(3)
    return 'Hello world!'

aio.run(app)

Now when I request index page (curl http://localhost:5000), everything goes right - I get Hello world after 3 seconds. But if I run 2 request simultaneously from different terminals, I get 500 error for both of them. At the same time server prints the following exception twice:

Error handling request
Traceback (most recent call last):
  File "/usr/lib/python3.5/site-packages/aiohttp/server.py", line 272, in start
    yield from self.handle_request(message, payload)
  File "/usr/lib/python3.5/site-packages/aiohttp/web.py", line 85, in handle_request
    resp = yield from handler(request)
  File "/usr/lib/python3.5/asyncio/coroutines.py", line 202, in coro
    res = yield from res
  File "/home/mars/test/flask_aiohttp/handler.py", line 18, in __call__
    response = yield from self.handle_request(request)
  File "/home/mars/test/flask_aiohttp/handler.py", line 119, in handle_request
    wsgi_response = yield from iterator
  File "/home/mars/test/flask_aiohttp/util.py", line 77, in __call__
    rv = yield from rv
  File "/usr/lib/python3.5/site-packages/flask/ctx.py", line 386, in __exit__
    self.auto_pop(exc_value)
  File "/usr/lib/python3.5/site-packages/flask/ctx.py", line 374, in auto_pop
    self.pop(exc)
  File "/usr/lib/python3.5/site-packages/flask/ctx.py", line 357, in pop
    % (rv, self)
AssertionError: Popped wrong request context.  (<RequestContext 'http://localhost:5000/hello' [GET] of main> instead of <RequestContext 'http://localhost:5000/hello' [GET] of main>)

What am I doing wrong? I use Python 3.5.0.