Hey folks When I run this code ```from prefect import flow t Prefect Community #ask-community

Hey, folks! When I run this code: ```from prefect ...

Nick Ackerman

10/03/2025, 5:17 PM

Hey, folks! When I run this code:

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from prefect import flow, task

@task
async def async_task():
    raise ValueError("aah!")

@task
def not_async_task():
    async_task.submit().result()

@flow
def my_flow():
    not_async_task()

my_flow()

I get the following error:

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File "/Users/nickackerman/code/python/practice/.venv/lib/python3.10/site-packages/prefect/transactions.py", line 624, in __aexit__
    await self.reset()
  File "/Users/nickackerman/code/python/practice/.venv/lib/python3.10/site-packages/prefect/transactions.py", line 492, in reset
    await parent.rollback()
TypeError: object bool can't be used in 'await' expression

Is this way of using Prefect futures together with async tasks not allowed for some reason? More details in 🧵

Nick Ackerman

10/03/2025, 5:19 PM

I'm on Prefect 3.4.21 but have seen this error in Prefect 3.3 as well. Interestingly, I don't get the "object bool can't be used in 'await' expression" error when I run this. So something seems different about using the task future in a flow versus in a task.

Copy code

from prefect import flow, task

@task
async def async_task():
    raise ValueError("aah!")

@flow
def my_flow():
    async_task.submit().result()

my_flow()

Nate

10/03/2025, 5:28 PM

hmm this looks like a bug related to nested task transactions

🙏 1

Nate

10/03/2025, 5:28 PM

taking a look

Nate

10/03/2025, 5:45 PM

https://github.com/PrefectHQ/prefect/pull/19097

Nate

10/03/2025, 6:43 PM

thanks for raising @Nick Ackerman -

prefect==3.4.22

is out now with the fix, running your example now raises the

ValueError

as you probably expected copying your original snippet:

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pbpaste | uv run --with prefect==3.4.22 -

...

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File "<string>", line 5, in async_task
ValueError: aah!

❤️ 1

Nick Ackerman

10/03/2025, 8:37 PM

This is amazing - thank you so much, Nate!

Nate

10/03/2025, 8:38 PM

catjam

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