diff --git a/skin/classic/treestyletab/sidebar/sidebar.css b/skin/classic/treestyletab/sidebar/sidebar.css
index 370fa82d..6f01e49c 100644
--- a/skin/classic/treestyletab/sidebar/sidebar.css
+++ b/skin/classic/treestyletab/sidebar/sidebar.css
@@ -471,6 +471,11 @@ tabbrowser[treestyletab-mode="vertical"]
   .tab-background {
 	margin: 0 -5px;
 }
+.tabbrowser-tabs[treestyletab-mode="vertical"]
+  .tabbrowser-tab[pinned]
+  .tab-background {
+	margin: 0;
+}