diff --git a/browser-features/chrome/common/ui-custom/styles/css/options/treestyletab.css b/browser-features/chrome/common/ui-custom/styles/css/options/treestyletab.css
index 62d097385a07f..336d8a76a5ae0 100644
--- a/browser-features/chrome/common/ui-custom/styles/css/options/treestyletab.css
+++ b/browser-features/chrome/common/ui-custom/styles/css/options/treestyletab.css
@@ -23,7 +23,7 @@
 vbox#sidebar-box[sidebarcommand="treestyletab_piro_sakura_ne_jp-sidebar-action"] {
   position: relative !important;
   clip-path: inset(0) !important;
-  z-index: 1 !important;
+  z-index: 1000 !important;
 }
 
 /*close*/
@@ -55,7 +55,3 @@ vbox#sidebar-box[sidebarcommand="treestyletab_piro_sakura_ne_jp-sidebar-action"]
     (var(--max-treestyletab-size) - var(--min-treestyletab-size)) * -1
   ) !important;
 }
-
-#sidebar-box[sidebarcommand="treestyletab_piro_sakura_ne_jp-sidebar-action"] {
-  z-index: 1000 !important;
-}