diff --git a/fastapi/dependencies/utils.py b/fastapi/dependencies/utils.py
index db55f9667..4c71b7cf0 100644
--- a/fastapi/dependencies/utils.py
+++ b/fastapi/dependencies/utils.py
@@ -637,14 +637,12 @@ async def solve_dependencies(
         elif is_coroutine_callable(call):
             solved = await call(**solved_result.values)
         else:
-            stack = request.scope.get("fastapi_astack")
-            assert isinstance(stack, AsyncExitStack)
             called = await run_in_threadpool(call, **solved_result.values)
             if hasattr(called, "__aenter__"):
-                solved = await stack.enter_async_context(called)
+                solved = await async_exit_stack.enter_async_context(called)
             elif hasattr(called, "__enter__"):
                 cm = contextmanager_in_threadpool(called)
-                solved = await stack.enter_async_context(cm)
+                solved = await async_exit_stack.enter_async_context(cm)
             else:
                 solved = called
         if sub_dependant.name is not None: