diff --git a/content/treestyletab/treestyletab.css b/content/treestyletab/treestyletab.css
index 4ec7184a..f408b659 100644
--- a/content/treestyletab/treestyletab.css
+++ b/content/treestyletab/treestyletab.css
@@ -74,13 +74,21 @@ tabbrowser[treestyletab-mode="vertical"] .tabs-stack > *:first-child + * > hbox:
 	-moz-box-flex: 1 !important;
 }
 
-.tabbrowser-tabs[treestyletab-mode="vertical"]
-	.tabbrowser-tab:not([treestyletab-removed="true"]):not([pinned]),
-.tabbrowser-tabs[treestyletab-mode="vertical"]
-	.tabbrowser-tab:not([treestyletab-removed="true"]):not([fadein]) {
-	max-width: none !important;
+/**
+ * Firefox 4.0 finishes opening and closing processes of tabs by its
+ * "transitionend" events about max-width property. I think this is very
+ * dirty and specific implementation but it won't fixed.
+ * (See: https://bugzilla.mozilla.org/show_bug.cgi?id=585417#c3 )
+ * So we have to define max-width for both states [fadein] (means "completely
+ * opened") and :not([fadein]) (means "in opening/removing process".
+ */
+.tabbrowser-tabs[treestyletab-mode="vertical"] .tabbrowser-tab:not([pinned]) {
+	max-width: 65000px !important;
 	min-width: 1px !important;
 }
+.tabbrowser-tabs[treestyletab-mode="vertical"] .tabbrowser-tab:not([pinned])[fadein] {
+	max-width: 65001px !important;
+}
 
 /* pinned tabs on Firefox 4.0 */
 .tabbrowser-tabs[treestyletab-mode="vertical"]
diff --git a/content/treestyletab/treestyletabbrowser.js b/content/treestyletab/treestyletabbrowser.js
index ba2d0ee1..2103e015 100644
--- a/content/treestyletab/treestyletabbrowser.js
+++ b/content/treestyletab/treestyletabbrowser.js
@@ -278,7 +278,6 @@ TreeStyleTabBrowser.prototype = {
 		b.mTabContainer.addEventListener('TabMove',        this, true);
 		b.mTabContainer.addEventListener('SSTabRestoring', this, true);
 		b.mTabContainer.addEventListener('SSTabRestored',  this, true);
-		b.mTabContainer.addEventListener('transitionend',  this, true);
 		b.mTabContainer.addEventListener('DOMAttrModified', this, true);
 		b.mTabContainer.addEventListener('mouseover', this, true);
 		b.mTabContainer.addEventListener('mouseout',  this, true);
@@ -1565,7 +1564,6 @@ TreeStyleTabBrowser.prototype = {
 		b.mTabContainer.removeEventListener('TabMove',        this, true);
 		b.mTabContainer.removeEventListener('SSTabRestoring', this, true);
 		b.mTabContainer.removeEventListener('SSTabRestored',  this, true);
-		b.mTabContainer.removeEventListener('transitionend',  this, true);
 		b.mTabContainer.removeEventListener('DOMAttrModified', this, true);
 		b.mTabContainer.removeEventListener('mouseover', this, true);
 		b.mTabContainer.removeEventListener('mouseout',  this, true);
@@ -1917,9 +1915,6 @@ TreeStyleTabBrowser.prototype = {
 			case 'SSTabRestored':
 				return this.onTabRestored(aEvent);
 
-			case 'transitionend':
-				return this.onTabAnimationEnd(aEvent);
-
 			case 'DOMAttrModified':
 				return this.onDOMAttrModified(aEvent);
 
@@ -2830,25 +2825,6 @@ TreeStyleTabBrowser.prototype = {
 			TreeStyleTabService.restoringTree = TreeStyleTabService.getRestoringTabsCount() > 0;
 	},
  
-	onTabAnimationEnd : function TSTBrowser_onTabAnimationEnd(aEvent) 
-	{
-		/*
-			"transitionend" event isn't fired multiplly, so, Firefox's
-			default handler possibly fails to handle animation end
-			because it watches only "max-width" property.
-			For safety, I decided to clean up all of removing tabs
-			by any animation end.
-		*/
-		var tab = aEvent.target;
-		var b = this.browser;
-		if (tab.localName == 'tab' && b) {
-			if (tab.getAttribute('fadein') == 'true')
-				b.tabContainer._handleNewTab(tab);
-			else if (b._removingTabs.indexOf(tab) > -1)
-				b._endRemoveTab(tab);
-		}
-	},
- 
 	onDOMAttrModified : function TSTBrowser_onDOMAttrModified(aEvent) 
 	{
 		switch (aEvent.attrName)