diff --git a/skin/classic/treestyletab/metal/Darwin.css b/skin/classic/treestyletab/metal/Darwin.css
index 1d0dad8b..88c149c2 100644
--- a/skin/classic/treestyletab/metal/Darwin.css
+++ b/skin/classic/treestyletab/metal/Darwin.css
@@ -9,6 +9,12 @@
 	padding-right: 0 !important;
 }
 
+.tabbrowser-tabs[treestyletab-mode="vertical"]
+  .tabs-newtab-button
+  .toolbarbutton-icon {
+	width: auto !important;
+}
+
 .tabbrowser-strip[treestyletab-mode="vertical"] {
 	border-bottom: 0 none !important;
 }