diff --git a/omeroweb/webclient/tree.py b/omeroweb/webclient/tree.py
index 87c67f565b..1190b9aa80 100644
--- a/omeroweb/webclient/tree.py
+++ b/omeroweb/webclient/tree.py
@@ -555,8 +555,10 @@ def _marshal_image(
         image_id, archived, name, owner_id, permissions, fileset_id = row
     else:
         # Likely this is being called by external code
-        warnings.warn("_marshal_image() is a 'private' function; "
-                      "row should have 6 elements", DeprecationWarning),
+        warnings.warn(
+            "_marshal_image() is a 'private' function; " "row should have 6 elements",
+            DeprecationWarning,
+        ),
         image_id, name, owner_id, permissions, fileset_id = row
         archived = False
     image = dict()