diff --git a/combo/public/static/js/combo.public.js b/combo/public/static/js/combo.public.js
index 05b05642..0780b223 100644
--- a/combo/public/static/js/combo.public.js
+++ b/combo/public/static/js/combo.public.js
@@ -220,6 +220,9 @@ $(function() {
       return;
     }
     var $cell_title = $cell.find('> div > h2:first-child');
+    if ($cell_title.attr('aria-expanded') !== undefined) {  // already prepared
+      return;
+    }
     $cell_title.attr('tabindex', '0');
     $cell_title.attr('role', 'button');
     function set_aria_expanded() {