diff --git a/dangerzone/gui/main_window.py b/dangerzone/gui/main_window.py
index f1395a7..cd4a1f9 100644
--- a/dangerzone/gui/main_window.py
+++ b/dangerzone/gui/main_window.py
@@ -1,10 +1,10 @@
 import logging
 import os
-from pathlib import Path
 import platform
 import tempfile
 import typing
 from multiprocessing.pool import ThreadPool
+from pathlib import Path
 from typing import List, Optional
 
 # FIXME: See https://github.com/freedomofpress/dangerzone/issues/320 for more details.
@@ -591,7 +591,7 @@ class ContentWidget(QtWidgets.QWidget):
             os_release_path = Path("/etc/os-release")
             if os_release_path.exists():
                 os_release = os_release_path.read_text()
-                if 'Ubuntu 20.04' in os_release or 'focal' in os_release:
+                if "Ubuntu 20.04" in os_release or "focal" in os_release:
                     self.warning_label = QtWidgets.QLabel(WARNING_MESSAGE)
                     self.warning_label.setWordWrap(True)
                     self.warning_label.setProperty("style", "warning")