diff --git a/content/treestyletab/treestyletab-3.1.css b/content/treestyletab/treestyletab-3.1.css
index 65510613..c7ae056a 100644
--- a/content/treestyletab/treestyletab-3.1.css
+++ b/content/treestyletab/treestyletab-3.1.css
@@ -1,6 +1,6 @@
 @namespace url("http://www.mozilla.org/keymaster/gatekeeper/there.is.only.xul");
 @namespace html url("http://www.w3.org/1999/xhtml");
 
-tabbrowser[treestyletab-mode="vertical"] .tabs-container > .tabbrowser-arrowscrollbox {
+tabbrowser .tabs-container > .tabbrowser-arrowscrollbox {
 	-moz-binding: url("chrome://treestyletab/content/treestyletab.xml#tabbrowser-arrowscrollbox");
 }
diff --git a/content/treestyletab/treestyletab.xml b/content/treestyletab/treestyletab.xml
index f71f28e0..b21f5b31 100644
--- a/content/treestyletab/treestyletab.xml
+++ b/content/treestyletab/treestyletab.xml
@@ -16,13 +16,15 @@
 		extends="chrome://browser/content/tabbrowser.xml#tabbrowser-arrowscrollbox">
 		<handlers>
 			<handler event="underflow"><![CDATA[
-				if (event.detail != 0) return; // Ignore horizontal events
 				var tabs = document.getBindingParent(this);
+				if ((event.detail == 0) == (tabs.getAttribute('orient') == 'horizontal'))
+					return;
 				tabs.removeAttribute("overflow");
 			]]></handler>
 			<handler event="overflow"><![CDATA[
-				if (event.detail != 0) return; // Ignore horizontal events
 				var tabs = document.getBindingParent(this);
+				if ((event.detail == 0) == (tabs.getAttribute('orient') == 'horizontal'))
+					return;
 				tabs.setAttribute("overflow", "true");
 				this.scrollBoxObject.ensureElementIsVisible(tabs.selectedItem);
 			]]></handler>
diff --git a/content/treestyletab/treestyletabbrowser.js b/content/treestyletab/treestyletabbrowser.js
index 05e95dd3..e64e1f88 100644
--- a/content/treestyletab/treestyletabbrowser.js
+++ b/content/treestyletab/treestyletabbrowser.js
@@ -123,6 +123,8 @@ TreeStyleTabBrowser.prototype = {
 		b.mTabContainer.addEventListener('select', this, true);
 		b.mTabContainer.addEventListener('scroll', this, true);
 
+		var container = document.getAnonymousElementByAttribute(b.mTabContainer, 'class', 'tabs-container');
+		if (container) container.removeAttribute('overflow');
 
 		/* Closing collapsed last tree breaks selected tab.
 		   To solve this problem, I override the setter to