diff --git a/content/treestyletab/treestyletab.css b/content/treestyletab/treestyletab.css
index 0432bab7..c6612b14 100644
--- a/content/treestyletab/treestyletab.css
+++ b/content/treestyletab/treestyletab.css
@@ -492,17 +492,17 @@ toolbar.treestyletab-tabbar-toolbar-ready:not([nowindowdrag="true"]),
 
 /* horizontal tab bar */
 .tabbrowser-tabs[treestyletab-mode="horizontal"]
-  .tabbrowser-tab:not([treestyletab-nest="0"]) + .tabbrowser-tab[treestyletab-nest="0"],
+  .tabbrowser-tab:not([treestyletab-nest="0"]):not([hidden="true"]) + .tabbrowser-tab[treestyletab-nest="0"],
 .tabbrowser-tabs[treestyletab-mode="horizontal"]
-  .tabbrowser-tab[treestyletab-nest="0"] + .tabbrowser-tab[treestyletab-nest="0"][treestyletab-children] {
+  .tabbrowser-tab[treestyletab-nest="0"]:not([hidden="true"]) + .tabbrowser-tab[treestyletab-nest="0"][treestyletab-children] {
 	margin-left: 0.8em !important;
 }
 
 /* vertical tab bar */
 .tabbrowser-tabs[treestyletab-mode="vertical"][treestyletab-max-tree-level="0"]
-  .tabbrowser-tab:not([treestyletab-nest="0"]) + .tabbrowser-tab[treestyletab-nest="0"],
+  .tabbrowser-tab:not([treestyletab-nest="0"]):not([hidden="true"]) + .tabbrowser-tab[treestyletab-nest="0"],
 .tabbrowser-tabs[treestyletab-mode="vertical"][treestyletab-max-tree-level="0"]
-  .tabbrowser-tab[treestyletab-nest="0"] + .tabbrowser-tab[treestyletab-nest="0"][treestyletab-children] {
+  .tabbrowser-tab[treestyletab-nest="0"]:not([hidden="true"]) + .tabbrowser-tab[treestyletab-nest="0"][treestyletab-children] {
 	margin-top: 0.8em !important;
 }