diff --git a/tests/get_browser.py b/tests/get_browser.py
index 3bead1e73..a798f59d3 100644
--- a/tests/get_browser.py
+++ b/tests/get_browser.py
@@ -45,7 +45,7 @@ def get_browser(browser_name, config=None, **kwargs):
         )
 
     elif browser_name == "flask":
-        app = kwargs.pop('app', app)
+        app = kwargs.pop("app", app)
         return Browser("flask", **kwargs)
 
     elif browser_name == "zope.testbrowser":