The asyncio cancel is convenient but can be really deceiving. If you want to reliably propagate the cancel across the wire, you likely have to invoke new await-

The asyncio cancel is convenient but can be really deceiving. If you want to reliably propagate the cancel across the wire, you likely have to invoke new await-calls inside your CancelledError-block. But doing this requires you to re-await the cancelled function again! async def process(): try: await db.slow_operation() except CancelledError: synchronous_functions_work() await db.cancel() # This future will not complete on timeout p = process() try: await asyncio.wait_for(p, timeout=1) except TimeoutError: await p # Required for db.cancel() to run!!! Now fire-and-forget on a timeout is perhaps the most reasonable approach, otherwise you'd get timeout on timeouts, so better implementation would be to restart p without awaiting it, or putting it on a background cancel-list. But it can be really confusing when you are not aware of this behavior. Edit: Seems they actually fixed/changed this in 3.7: https://bugs.python.org/issue32751 https://bugs.python.org/issue32751. So instead you have to write robust except-blocks that must never timeout.