diff --git a/chrome.manifest b/chrome.manifest
index e0a3a6ea..8ce00935 100644
--- a/chrome.manifest
+++ b/chrome.manifest
@@ -1,7 +1,7 @@
 content	treestyletab	jar:chrome/treestyletab.jar!/content/treestyletab/
 
 overlay	chrome://browser/content/browser.xul	chrome://treestyletab/content/treestyletab.xul
-overlay	chrome://browser/content/bookmarks/bookmarksPanel.xul	chrome://treestyletab/content/bookmarksOverlay.xul
+overlay	chrome://browser/content/browser.xul	chrome://treestyletab/content/treestyletab-fx3.xul	appversion>=3.0overlay	chrome://browser/content/bookmarks/bookmarksPanel.xul	chrome://treestyletab/content/bookmarksOverlay.xul
 overlay	chrome://multipletab/content/config.xul	chrome://treestyletab/content/multipletabConfigOverlay.xul
 
 style chrome://browser/content/browser.xul chrome://treestyletab/content/treestyletab-3.5.css appversion>=3.1b3pre
diff --git a/content/treestyletab/treestyletab-fx3.xul b/content/treestyletab/treestyletab-fx3.xul
new file mode 100644
index 00000000..6d5ac5b5
--- /dev/null
+++ b/content/treestyletab/treestyletab-fx3.xul
@@ -0,0 +1,5 @@
+<?xml version="1.0"?>
+<overlay xmlns="http://www.mozilla.org/keymaster/gatekeeper/there.is.only.xul">
+<stringbundle id="treestyletab-tabbrowserBundle"
+	src="chrome://browser/locale/tabbrowser.properties"/>
+</overlay>
diff --git a/content/treestyletab/treestyletab.js b/content/treestyletab/treestyletab.js
index da576a38..b37d65a9 100644
--- a/content/treestyletab/treestyletab.js
+++ b/content/treestyletab/treestyletab.js
@@ -228,6 +228,14 @@ var TreeStyleTabService = {
 		return this._stringbundle;
 	},
 	_stringbundle : null,
+
+	get tabbrowserBundle() {
+		if (!this._tabbrowserBundle) {
+			this._tabbrowserBundle = document.getElementById('treestyletab-tabbrowserBundle');
+		}
+		return this._tabbrowserBundle;
+	},
+	_tabbrowserBundle : null,
 	
 /* API */ 
 	
@@ -2029,24 +2037,40 @@ catch(e) {
 		else
 			tabs = this.cleanUpTabsArray(tabs.concat(descendant));
 
-		var max = tabs.length;
-		if (!max) return;
-
-		b.__treestyletab__closedTabsNum = max;
-		if (
-			max > 1 &&
-			!b.warnAboutClosingTabs(true)
-			) {
-			b.__treestyletab__closedTabsNum = 0;
+		if (!this.warnAboutClosingTabs(tabs.length))
 			return;
-		}
-		b.__treestyletab__closedTabsNum = 0;
 
 		for (var i = tabs.length-1; i > -1; i--)
 		{
 			b.removeTab(tabs[i]);
 		}
 	},
+	warnAboutClosingTabs : function(aTabsCount)
+	{
+		if (
+			aTabsCount <= 1 ||
+			this.getPref('browser.tabs.warnOnClose')
+			)
+			return true;
+		var promptService = Components
+							.classes['@mozilla.org/embedcomp/prompt-service;1']
+							.getService(Components.interfaces.nsIPromptService);
+		var checked = { value:true };
+		window.focus();
+		var shouldClose = promptService.confirmEx(window,
+				this.tabbrowserBundle.getString('tabs.closeWarningTitle'),
+				this.tabbrowserBundle.getFormattedString('tabs.closeWarningMultipleTabs', [aTabsCount]),
+				(promptService.BUTTON_TITLE_IS_STRING * promptService.BUTTON_POS_0) +
+				(promptService.BUTTON_TITLE_CANCEL * promptService.BUTTON_POS_1),
+				this.tabbrowserBundle.getString('tabs.closeButtonMultiple'),
+				null, null,
+				this.tabbrowserBundle.getString('tabs.closeWarningPromptMe'),
+				checked
+			) == 0;
+		if (shouldClose && !checked.value)
+			this.setPref('browser.tabs.warnOnClose', false);
+		return shouldClose;
+	},
 	
 	cleanUpTabsArray : function(aTabs) 
 	{
diff --git a/content/treestyletab/treestyletab.xul b/content/treestyletab/treestyletab.xul
index 3749db35..016d6844 100644
--- a/content/treestyletab/treestyletab.xul
+++ b/content/treestyletab/treestyletab.xul
@@ -48,6 +48,8 @@
 <stringbundleset id="stringbundleset">
 	<stringbundle id="treestyletab-stringbundle"
 		src="chrome://treestyletab/locale/treestyletab.properties"/>
+	<stringbundle id="treestyletab-tabbrowserBundle"
+		src="chrome://global/locale/tabbrowser.properties"/>
 </stringbundleset>
 
 <popupset id="mainPopupSet">
diff --git a/content/treestyletab/treestyletabbrowser.js b/content/treestyletab/treestyletabbrowser.js
index 58f11390..450e5838 100644
--- a/content/treestyletab/treestyletabbrowser.js
+++ b/content/treestyletab/treestyletabbrowser.js
@@ -465,13 +465,6 @@ TreeStyleTabBrowser.prototype = {
 			)
 		);
 
-		eval('b.warnAboutClosingTabs = '+
-			b.warnAboutClosingTabs.toSource().replace(
-				'var numTabs = ',
-				'var numTabs = this.__treestyletab__closedTabsNum || '
-			)
-		);
-
 		if ('_onDragEnd' in b) {
 			eval('b._onDragEnd = '+b._onDragEnd.toSource().replace(
 				'this._replaceTabWithWindow(',