diff --git a/qt/aqt/editor.py b/qt/aqt/editor.py
index 674b09274..1942f908d 100644
--- a/qt/aqt/editor.py
+++ b/qt/aqt/editor.py
@@ -321,7 +321,7 @@ require("anki/ui").loaded.then(() => require("anki/NoteEditor").instances[0].too
         class_attribute = "linkb" if rightside else "rounded"
 
         if not disables:
-            class_attribute += " perm"
+            class_attribute = f"{class_attribute} perm"
 
         return f"""<button tabindex=-1
                         {id_attribute_assignment}