diff --git a/docs_src/query_params_str_validations/tutorial015_an_py310.py b/docs_src/query_params_str_validations/tutorial015_an_py310.py
index 35f368094..05aadd714 100644
--- a/docs_src/query_params_str_validations/tutorial015_an_py310.py
+++ b/docs_src/query_params_str_validations/tutorial015_an_py310.py
@@ -1,7 +1,7 @@
 import random
 from typing import Annotated
 
-from fastapi import FastAPI
+from fastapi import FastAPI, HTTPException
 from pydantic import AfterValidator
 
 app = FastAPI()
@@ -25,6 +25,10 @@ async def read_items(
 ):
     if id:
         item = data.get(id)
+        if item is None:
+            raise HTTPException(
+                status_code=404, detail=f"Item with id '{id}' not found"
+            )
     else:
         id, item = random.choice(list(data.items()))
     return {"id": id, "name": item}