diff --git a/datasette/app.py b/datasette/app.py
index c940f6dc..b3292f60 100644
--- a/datasette/app.py
+++ b/datasette/app.py
@@ -1811,7 +1811,7 @@ class DatasetteRouter:
 
             # If you redirect with a // at the beginning, you end up with an open redirect, so
             # https://my.site//foo/ - will redirect to https://foo
-            path = re.sub(rb'^/+', b'/', path)
+            path = re.sub(rb"^/+", b"/", path)
 
             if request.scope["query_string"]:
                 path += b"?" + request.scope["query_string"]
diff --git a/tests/test_custom_pages.py b/tests/test_custom_pages.py
index 48b27e7b..ccc139ce 100644
--- a/tests/test_custom_pages.py
+++ b/tests/test_custom_pages.py
@@ -98,7 +98,8 @@ def test_custom_route_pattern_404(custom_pages_client):
     assert "<h1>Error 404</h1>" in response.text
     assert ">Oh no</" in response.text
 
+
 def test_custom_route_pattern_with_slash_slash_302(custom_pages_client):
     response = custom_pages_client.get("//nastyOpenRedirect/")
     assert response.status == 302
-    assert response.headers['location'] == "/nastyOpenRedirect"
+    assert response.headers["location"] == "/nastyOpenRedirect"