ok. I went further. First of all I was wrong in first example (calling twice the coroutine function). But it might still be a bug. we can't return value from coroutine decorated by db_session. As well I do not know if it's important but decorated with db_session async function are not seen as coroutine function. Here is a complete example import asyncio from pony.orm import Database, Required, db_session db = Database() class People(db.Entity): name = Required(str) db.bind(provider="sqlite", filename=":memory:") db.generate_mapping(create_tables=True) with db_session(): People(name="john") async def dummy_coro(): print("inside dummy coro") return "dummy" @db_session async def db_session_coro(): print("inside db_session coro") return "dummy" @db_session async def db_session_coro_with_query(): print("inside db_session coro with query") pp = People[1].to_dict() print(pp) return pp async def do_async(func): res = await func() print("result in do_async: ", res) return res def main(): loop = asyncio.get_event_loop() print(asyncio.iscoroutinefunction(dummy_coro)) # -> True print(asyncio.iscoroutinefunction(db_session_coro)) # -> False print(loop.run_until_complete(dummy_coro())) # -> inside dummy coro # -> dummy print(loop.run_until_complete(db_session_coro())) # -> inside dummy coro # -> None print(loop.run_until_complete(db_session_coro_with_query())) # -> inside dummy coro with query # -> {'id': 1, 'name': 'john'} # -> None loop.run_until_complete(do_async(dummy_coro)) # -> inside dummy coro # -> result in do_async: dummy loop.run_until_complete(do_async(db_session_coro)) # -> inside dummy coro # -> result in do_async: None loop.run_until_complete(do_async(db_session_coro_with_query)) # -> inside dummy coro with query # -> {'id': 1, 'name': 'john'} # -> result in do_async: None if __name__ == "__main__": main()