diff --git a/firefox/treestyletab.css b/firefox/treestyletab.css
index fd545ad..805f07d 100644
--- a/firefox/treestyletab.css
+++ b/firefox/treestyletab.css
@@ -10,3 +10,7 @@ tab-item {
   font-style: italic !important;
   text-decoration: underline;
 }
+
+tab-closebox {
+  display: none
+}