diff --git a/content/treestyletab/hacks.js b/content/treestyletab/hacks.js
index a287f523..f45de698 100644
--- a/content/treestyletab/hacks.js
+++ b/content/treestyletab/hacks.js
@@ -539,7 +539,7 @@ TreeStyleTabService.overrideExtensionsOnInitAfter = function() {
 
 		window.setTimeout(function() {
 			// correct broken appearance of the first tab
-			var t = gBrowser.treeStyleTab.getTabs(gBrowser).snapshotItem(0);
+			var t = gBrowser.treeStyleTab.getFirstTab(gBrowser);
 			gBrowser.treeStyleTab.initTabAttributes(t);
 			gBrowser.treeStyleTab.initTabContentsOrder(t);
 
diff --git a/content/treestyletab/treestyletab.js b/content/treestyletab/treestyletab.js
index 0d793456..c3e1be43 100644
--- a/content/treestyletab/treestyletab.js
+++ b/content/treestyletab/treestyletab.js
@@ -592,6 +592,15 @@ var TreeStyleTabService = {
 		return array;
 	},
  
+	getFirstTab : function(aTabBrowser) 
+	{
+		return this.evaluateXPath(
+				'descendant::xul:tab[1]',
+				aTabBrowser.mTabContainer,
+				XPathResult.FIRST_ORDERED_NODE_TYPE
+			).singleNodeValue;
+	},
+ 
 	getLastTab : function(aTabBrowser) 
 	{
 		return this.evaluateXPath(
diff --git a/content/treestyletab/treestyletabbrowser.js b/content/treestyletab/treestyletabbrowser.js
index d2405484..02cd7d3c 100644
--- a/content/treestyletab/treestyletabbrowser.js
+++ b/content/treestyletab/treestyletabbrowser.js
@@ -2650,7 +2650,7 @@ TreeStyleTabBrowser.prototype = {
 		var oldMargin = this.levelMargin;
 		var indent    = (oldMargin < 0 ? this.baseLebelMargin : oldMargin ) * nest;
 		var maxIndent = (
-				this.getTabs(b).snapshotItem(0).boxObject[this.invertedSizeProp] ||
+				this.getFirstTab(b).boxObject[this.invertedSizeProp] ||
 				b.mTabContainer.boxObject[this.invertedSizeProp]
 			) * 0.33;
 
@@ -3002,7 +3002,7 @@ TreeStyleTabBrowser.prototype = {
 		var tabSize           = lastVisible.boxObject[this.sizeProp];
 
 		if (lastPosition - parentPosition + tabSize > containerSize - tabSize) { // out of screen
-			var endPos = parentPosition - this.getTabs(b).snapshotItem(0).boxObject[this.positionProp] - tabSize * 0.5;
+			var endPos = parentPosition - this.getFirstTab(b).boxObject[this.positionProp] - tabSize * 0.5;
 			var endX = this.isVertical ? 0 : endPos ;
 			var endY = this.isVertical ? endPos : 0 ;
 			this.scrollTo(endX, endY);