If I create a coro from an async iterator, then wait_for it w/ a timeout, but shielded, so it won't get canceled, and then await upon it, it returns invalid data. See the attached test case. The reason I do the following is to make sure that an async iterator that I have written doesn't return data early, and needs to wait till later. If I didn't shield it, then the async iterator would get cancelled, and I don't want this. I'd expect either correct results to be returned, or an exception to be raised, but in this case, and the docs for wait_for ( https://docs.python.org/3/library/asyncio-task.html#asyncio.wait_for ), I'd expect the correct results to be returned. In the attached case, this is the results that I get: $python3.7 asyncitertc.py 3.7.5 (default, Oct 18 2019, 23:59:39) [Clang 7.0.2 (clang-700.1.81)] timed out yielding 1 results: None getting 2: 2 I do not have python 3.8 to test with.

Thanks for the report. Your example could be boiled down to the following: coro = asynciter() await coro await coro The second call incorrectly returns None but should raise an exception, double awaiting is a programming error. For regular async functions it raises "RuntimeError: cannot reuse already awaited coroutine"

 New changeset a96e06db77dcbd3433d39761ddb4615d7d96284a by Andrew Svetlov in branch 'master': bpo-39386: Prevent double awaiting of async iterator (GH-18081) https://github.com/python/cpython/commit/a96e06db77dcbd3433d39761ddb4615d7d96284a 

 New changeset 5cadd3fe3aead1b5bee1438dc03383d6739d4209 by Miss Islington (bot) in branch '3.8': bpo-39386: Prevent double awaiting of async iterator (GH-18081) https://github.com/python/cpython/commit/5cadd3fe3aead1b5bee1438dc03383d6739d4209 

 New changeset b76d5e9ee64b8ac861e856d8e41289c0977c75e1 by Miss Islington (bot) in branch '3.7': bpo-39386: Prevent double awaiting of async iterator (GH-18081) https://github.com/python/cpython/commit/b76d5e9ee64b8ac861e856d8e41289c0977c75e1 

 New changeset 925dc7fb1d0db85dc137afa4cd14211bf0d67414 by Nathaniel J. Smith in branch 'master': bpo-39606: allow closing async generators that are already closed (GH-18475) https://github.com/python/cpython/commit/925dc7fb1d0db85dc137afa4cd14211bf0d67414 

 New changeset 8dbdf5f275c6462bb522bcf3a29054239d72989d by Miss Islington (bot) in branch '3.8': [3.8] bpo-39606: allow closing async generators that are already closed (GH-18475) (GH-18501) https://github.com/python/cpython/commit/8dbdf5f275c6462bb522bcf3a29054239d72989d 

 New changeset f464edf3239f7867fe31c9cd238a68fb3b90feaa by Nathaniel J. Smith in branch '3.7': bpo-39606: allow closing async generators that are already closed (GH-18475) (GH-18502) https://github.com/python/cpython/commit/f464edf3239f7867fe31c9cd238a68fb3b90feaa