diff --git a/docs_src/custom_response/tutorial007_py39.py b/docs_src/custom_response/tutorial007_py39.py
index e2a53a2119..0c17ce40ee 100644
--- a/docs_src/custom_response/tutorial007_py39.py
+++ b/docs_src/custom_response/tutorial007_py39.py
@@ -1,3 +1,5 @@
+import asyncio
+
 from fastapi import FastAPI
 from fastapi.responses import StreamingResponse
 
@@ -6,6 +8,7 @@ app = FastAPI()
 
 async def fake_video_streamer():
     for i in range(10):
+        await asyncio.sleep(0)
         yield b"some fake video bytes"