diff --git a/content/treestyletab/hacks.js b/content/treestyletab/hacks.js
index 16bf3758..f6c3b2b2 100644
--- a/content/treestyletab/hacks.js
+++ b/content/treestyletab/hacks.js
@@ -93,7 +93,8 @@ TreeStyleTabService.overrideExtensionsOnInitBefore = function() {
 		flst.tb = gBrowser;
 		flst.tabBox = flst.tb.mTabBox;
 	}
-	if ('ensureTabIsVisible' in gBrowser.mTabContainer) {
+	if ('isTabVisible' in gBrowser.mTabContainer &&
+		'ensureTabIsVisible' in gBrowser.mTabContainer) {
 		function replaceHorizontalProps(aString)
 		{
 			return aString.replace(
@@ -110,15 +111,16 @@ TreeStyleTabService.overrideExtensionsOnInitBefore = function() {
 					]]>
 				)
 		}
-		eval('gBrowser.mTabContainer.isTabVisible = '+
-			replaceHorizontalProps(gBrowser.mTabContainer.isTabVisible.toSource())
-		);
 		eval('gBrowser.mTabContainer.ensureTabIsVisible = '+
 			replaceHorizontalProps(gBrowser.mTabContainer.ensureTabIsVisible.toSource().replace(
 				'tabhbox.boxObject.width < 250',
 				'$& && !gBrowser.treeStyleTab.isVertical'
 			))
 		);
+		if (!this.getTreePref('TMP.doNotUpdate.isTabVisible'))
+			eval('gBrowser.mTabContainer.isTabVisible = '+
+				replaceHorizontalProps(gBrowser.mTabContainer.isTabVisible.toSource())
+			);
 	}
 
 };
diff --git a/defaults/preferences/treestyletab.js b/defaults/preferences/treestyletab.js
index 693a7d0d..039f53e8 100644
--- a/defaults/preferences/treestyletab.js
+++ b/defaults/preferences/treestyletab.js
@@ -74,5 +74,8 @@ pref("browser.tabs.loadFolderAndReplace.override", false);
 pref("extensions.multipletab.show.multipletab-selection-item-removeTabSubTree", true);
 
 
+pref("extensions.treestyletab.TMP.doNotUpdate.isTabVisible", false);
+
+
 pref("extensions.treestyletab@piro.sakura.ne.jp.name", "chrome://treestyletab/locale/treestyletab.properties");
 pref("extensions.treestyletab@piro.sakura.ne.jp.description", "chrome://treestyletab/locale/treestyletab.properties");