diff --git a/nonebug/fixture.py b/nonebug/fixture.py
index 0853467..cbf32e0 100644
--- a/nonebug/fixture.py
+++ b/nonebug/fixture.py
@@ -1,4 +1,4 @@
-from contextlib import nullcontext, asynccontextmanager
+from contextlib import asynccontextmanager
 
 import pytest
 from async_asgi_testclient import TestClient
@@ -9,6 +9,11 @@
 from . import NONEBOT_INIT_KWARGS, NONEBOT_START_LIFESPAN
 
 
+@asynccontextmanager
+async def nullcontext():
+    yield
+
+
 @asynccontextmanager
 async def lifespan_ctx():
     import nonebot