diff --git a/content/treestyletab/treestyletab-tmp.css b/content/treestyletab/treestyletab-tmp.css
index a62ff957..3fffa31b 100644
--- a/content/treestyletab/treestyletab-tmp.css
+++ b/content/treestyletab/treestyletab-tmp.css
@@ -15,12 +15,13 @@
 
 :root[treestyletab-enable-compatibility-tmp="true"]
   tabbrowser[treestyletab-mode="vertical"] tabs[flowing] > * .tabs-frame {
-	overflow-x: hidden !important;
-	overflow-y: auto !important;
+	-moz-box-flex: 1 !important;
 }
 
 :root[treestyletab-enable-compatibility-tmp="true"]
-  tabbrowser[treestyletab-mode="vertical"] tabs[flowing] > * .tabs-frame {
+  tabbrowser[treestyletab-mode="vertical"] tabs[flowing] > * .tabs-frame > .scrollbox-innerbox {
+	overflow-x: hidden !important;
+	overflow-y: auto !important;
 	-moz-box-flex: 1 !important;
 }
 
diff --git a/content/treestyletab/treestyletab.css b/content/treestyletab/treestyletab.css
index 0ff6867d..c6cd56f3 100644
--- a/content/treestyletab/treestyletab.css
+++ b/content/treestyletab/treestyletab.css
@@ -44,9 +44,10 @@ tabbrowser[treestyletab-mode="vertical"] .tab-drop-indicator-bar {
 	margin: 0;
 }
 
-tabbrowser[treestyletab-mode="vertical"] .tabbrowser-arrowscrollbox > scrollbox {
+tabbrowser[treestyletab-mode="vertical"] .tabbrowser-arrowscrollbox > scrollbox > .scrollbox-innerbox {
 	overflow-x: hidden !important;
 	overflow-y: auto !important;
+	-moz-box-flex: 1 !important;
 }
 
 /* for Firefox 3.0 (not 3.5 and later!) */