diff --git a/content/treestyletab/treestyletab.css b/content/treestyletab/treestyletab.css
index 01af24f2..0b3ed19e 100644
--- a/content/treestyletab/treestyletab.css
+++ b/content/treestyletab/treestyletab.css
@@ -91,7 +91,7 @@ tabbrowser[treestyletab-mode="vertical"] .tabs-stack > *:first-child + * > hbox:
 .tabbrowser-tabs[treestyletab-mode="vertical"]
 	.tabbrowser-tab[pinned="true"] {
 	position: fixed !important;
-	z-index: 100 !important;
+	z-index: 100;
 	width: 24px !important;
 	height: 24px !important;
 }