diff --git a/skin/classic/treestyletab/sidebar/sidebar-base.css b/skin/classic/treestyletab/sidebar/sidebar-base.css
index 9d16387c..f8637e3d 100644
--- a/skin/classic/treestyletab/sidebar/sidebar-base.css
+++ b/skin/classic/treestyletab/sidebar/sidebar-base.css
@@ -115,6 +115,11 @@ tabbrowser[treestyletab-mode="vertical"]
 	padding: 0 !important;
 	line-height: 1 !important;
 }
+.tabbrowser-tabs[treestyletab-mode="vertical"]
+  :-moz-any(.tab-throbber[pinned],
+            .tab-icon-image[pinned]) {
+	margin: 0 !important;
+}
 .tabbrowser-tabs[treestyletab-mode="vertical"]
   .tabbrowser-tab[pinned]
   .tab-stack {