diff --git a/jupyter_server/base/handlers.py b/jupyter_server/base/handlers.py
index 1dcc282bc..bd4426268 100644
--- a/jupyter_server/base/handlers.py
+++ b/jupyter_server/base/handlers.py
@@ -1194,11 +1194,7 @@ class ExtensionAppsHandler(JupyterHandler):
     @allow_unauthenticated
     def get(self) -> None:
         self.set_header("Content-Type", "application/json")
-        self.finish(
-            json.dumps(
-                self.serverapp.extension_manager.extension_web_apps()
-            )
-        )
+        self.finish(json.dumps(self.serverapp.extension_manager.extension_web_apps()))
 
 
 # -----------------------------------------------------------------------------
diff --git a/jupyter_server/extension/manager.py b/jupyter_server/extension/manager.py
index 6eb0d0114..d4bcccfd5 100644
--- a/jupyter_server/extension/manager.py
+++ b/jupyter_server/extension/manager.py
@@ -3,8 +3,8 @@
 from __future__ import annotations
 
 import importlib
-from itertools import starmap
 import re
+from itertools import starmap
 
 from tornado.gen import multi
 from traitlets import Any, Bool, Dict, HasTraits, Instance, List, Unicode, default, observe
@@ -14,8 +14,7 @@
 from .config import ExtensionConfigManager
 from .utils import ExtensionMetadataError, ExtensionModuleNotFound, get_loader, get_metadata
 
-
-RE_SLASH = x = re.compile('/+')  # match any number of slashes
+RE_SLASH = x = re.compile("/+")  # match any number of slashes
 
 
 class ExtensionPoint(HasTraits):
@@ -306,11 +305,12 @@ def extension_web_apps(self):
         extensions which provide a default_url (i.e. a web application).
         """
         return {
-            app.name: RE_SLASH.sub('/', f'{self.serverapp.base_url}/{app.default_url}')
+            app.name: RE_SLASH.sub("/", f"{self.serverapp.base_url}/{app.default_url}")
             for extension_apps in self.serverapp.extension_manager.extension_apps.values()
             # filter out extensions that do not provide a default_url OR
             # set it to the root endpoint.
-            for app in extension_apps if getattr(app, 'default_url', '/') != '/'
+            for app in extension_apps
+            if getattr(app, "default_url", "/") != "/"
         }
 
     @property
diff --git a/tests/extension/mockextensions/app.py b/tests/extension/mockextensions/app.py
index a221eb2f5..390a93455 100644
--- a/tests/extension/mockextensions/app.py
+++ b/tests/extension/mockextensions/app.py
@@ -50,7 +50,7 @@ class MockExtensionApp(ExtensionAppJinjaMixin, ExtensionApp):
     static_paths = [STATIC_PATH]  # type:ignore[assignment]
     mock_trait = Unicode("mock trait", config=True)
     loaded = False
-    default_url = '/mockextension'
+    default_url = "/mockextension"
 
     serverapp_config = {"jpserver_extensions": {"tests.extension.mockextensions.mock1": True}}
 
diff --git a/tests/extension/test_app.py b/tests/extension/test_app.py
index e99b30d18..62f03af2c 100644
--- a/tests/extension/test_app.py
+++ b/tests/extension/test_app.py
@@ -198,10 +198,11 @@ async def test_extension_web_apps(jp_serverapp):
 
     # there should be (at least) two extension applications
     assert set(jp_serverapp.extension_manager.extension_apps) == {
-        'tests.extension.mockextensions', 'jupyter_server_terminals'
+        "tests.extension.mockextensions",
+        "jupyter_server_terminals",
     }
 
     # but only one extension web application
     assert jp_serverapp.extension_manager.extension_web_apps == {
-        'mockextension': '/a%40b/mockextension'
+        "mockextension": "/a%40b/mockextension"
     }