diff --git a/content/treestyletab/treestyletabbrowser.js b/content/treestyletab/treestyletabbrowser.js
index 34586631..5c670d2d 100644
--- a/content/treestyletab/treestyletabbrowser.js
+++ b/content/treestyletab/treestyletabbrowser.js
@@ -2276,8 +2276,15 @@ TreeStyleTabBrowser.prototype = {
 
 			// toolbar customizing on Firefox 4 or later
 			case 'beforecustomization':
+				this.toolbarCustomizing = true;
 				return this.syncDestroyTabbar();
 			case 'aftercustomization':
+				// Ignore it, because 'aftercustomization' fired not
+				// following to 'beforecustomization' is invalid.
+				// Personal Titlebar addon (or others) fires a fake
+				// event on its startup process.
+				if (!this.toolbarCustomizing) return;
+				this.toolbarCustomizing = false;
 				return this.syncReinitTabbar();
 			case 'customizationchange':
 				return this.updateCustomizedTabsToolbar();