diff --git a/src/prometheus_fastapi_instrumentator/instrumentation.py b/src/prometheus_fastapi_instrumentator/instrumentation.py
index f6860ac..17e51db 100644
--- a/src/prometheus_fastapi_instrumentator/instrumentation.py
+++ b/src/prometheus_fastapi_instrumentator/instrumentation.py
@@ -3,9 +3,19 @@
 import os
 import re
 import warnings
-from enum import Enum
-from typing import Any, Awaitable, Callable, List, Optional, Sequence, Union, cast, Tuple
 from base64 import b64encode
+from enum import Enum
+from typing import (
+    Any,
+    Awaitable,
+    Callable,
+    List,
+    Optional,
+    Sequence,
+    Tuple,
+    Union,
+    cast,
+)
 
 from fastapi import FastAPI, HTTPException
 from prometheus_client import (
@@ -248,7 +258,7 @@ def expose(
 
             tags (List[str], optional): If you manage your routes with tags.
                 Defaults to None.
-            
+
             basic_auth (Tuple[str, str], optional): username and password for
                 HTTP basic authentication. Disabled if None.
 
@@ -264,18 +274,22 @@ def expose(
         authorization_value = None
         if basic_auth is not None:
             username, password = basic_auth
-            encoded_cred = b64encode(f'{username}:{password}'.encode('utf-8')).decode('ascii')
+            encoded_cred = b64encode(f"{username}:{password}".encode("utf-8")).decode(
+                "ascii"
+            )
             authorization_value = f"Basic {encoded_cred}"
 
         @app.get(endpoint, include_in_schema=include_in_schema, tags=tags, **kwargs)
         def metrics(request: Request) -> Response:
             """Endpoint that serves Prometheus metrics."""
 
-            authorization_header = request.headers.get('authorization', None)
+            authorization_header = request.headers.get("authorization", None)
             if authorization_header != authorization_value:
                 raise HTTPException(
                     status_code=401,
-                    headers={'WWW-Authenticate': 'Basic realm="Access to metrics endpoint"'}
+                    headers={
+                        "WWW-Authenticate": 'Basic realm="Access to metrics endpoint"'
+                    },
                 )
 
             ephemeral_registry = self.registry
diff --git a/tests/test_instrumentator_expose.py b/tests/test_instrumentator_expose.py
index 6437fbd..34d78f4 100644
--- a/tests/test_instrumentator_expose.py
+++ b/tests/test_instrumentator_expose.py
@@ -80,8 +80,8 @@ def test_expose_custom_path():
 
 
 def test_expose_basic_auth():
-    username = 'hello'
-    password = 'mom'
+    username = "hello"
+    password = "mom"
     app = create_app()
     Instrumentator().instrument(app).expose(app, basic_auth=(username, password))
     client = TestClient(app)