diff --git a/asgiref/sync.py b/asgiref/sync.py
index f263a432..4427fc2a 100644
--- a/asgiref/sync.py
+++ b/asgiref/sync.py
@@ -478,6 +478,8 @@ async def __call__(self, *args: _P.args, **kwargs: _P.kwargs) -> _R:
                     pass
             except IndexError:
                 pass
+            if exec_coro.done():
+                raise
             if cancel_parent:
                 exec_coro.cancel()
             ret = await exec_coro