diff --git a/fastapi/encoders.py b/fastapi/encoders.py
index 369defe0f2267..f64e4b86ea3b4 100644
--- a/fastapi/encoders.py
+++ b/fastapi/encoders.py
@@ -71,7 +71,7 @@ def jsonable_encoder(
             sqlalchemy_safe=sqlalchemy_safe,
         )
     if dataclasses.is_dataclass(obj):
-        obj_dict =  dataclasses.asdict(obj)
+        obj_dict = dataclasses.asdict(obj)
         return jsonable_encoder(
             obj_dict,
             exclude_none=exclude_none,
diff --git a/tests/test_serialize_response_dataclass.py b/tests/test_serialize_response_dataclass.py
index 8583fac1aadd5..1e3bf3b28bcc3 100644
--- a/tests/test_serialize_response_dataclass.py
+++ b/tests/test_serialize_response_dataclass.py
@@ -1,8 +1,9 @@
-from typing import List, Optional
+from dataclasses import dataclass
 from datetime import datetime
+from typing import List, Optional
+
 from fastapi import FastAPI
 from fastapi.testclient import TestClient
-from dataclasses import dataclass
 
 app = FastAPI()
 
@@ -172,7 +173,22 @@ def test_no_response_model_objectlist():
     response = client.get("/items/no-response-model/objectlist")
     response.raise_for_status()
     assert response.json() == [
-        {"name": "foo", "date": datetime(2021, 7, 26).isoformat(), "price": None, "owner_ids": None},
-        {"name": "bar", "date": datetime(2021, 7, 26).isoformat(), "price": 1.0, "owner_ids": None},
-        {"name": "baz", "date": datetime(2021, 7, 26).isoformat(), "price": 2.0, "owner_ids": [1, 2, 3]},
+        {
+            "name": "foo",
+            "date": datetime(2021, 7, 26).isoformat(),
+            "price": None,
+            "owner_ids": None,
+        },
+        {
+            "name": "bar",
+            "date": datetime(2021, 7, 26).isoformat(),
+            "price": 1.0,
+            "owner_ids": None,
+        },
+        {
+            "name": "baz",
+            "date": datetime(2021, 7, 26).isoformat(),
+            "price": 2.0,
+            "owner_ids": [1, 2, 3],
+        },
     ]