diff --git a/content/treestyletab/windowHelper.js b/content/treestyletab/windowHelper.js
index 2edf6b38..b75cbe67 100644
--- a/content/treestyletab/windowHelper.js
+++ b/content/treestyletab/windowHelper.js
@@ -272,12 +272,6 @@ var TreeStyleTabWindowHelper = {
 			};
 		}, this);
 
-		window.__treestyletab__duplicateTabIn = window.duplicateTabIn;
-		window.duplicateTabIn = function(aTab, where, delta) {
-			gBrowser.treeStyleTab.onBeforeTabDuplicate(aTab, where, delta);
-			return window.__treestyletab__duplicateTabIn.call(this, aTab, where, delta);
-		};
-
 		window.__treestyletab__BrowserGoHome = window.BrowserGoHome;
 		window.BrowserGoHome = function(aEvent) {
 			aEvent = TreeStyleTabService.onBeforeGoHome(aEvent, gBrowser);
diff --git a/modules/utils.js b/modules/utils.js
index 62a1657b..ec5f8294 100644
--- a/modules/utils.js
+++ b/modules/utils.js
@@ -799,4 +799,11 @@ prefs.addPrefListener(TreeStyleTabUtils);
 			TabAttributesInternal._skipAttrs.add(name);
 		});
 	}
+
+	let { SessionStore } = Cu.import('resource:///modules/sessionstore/SessionStore.jsm', {});
+	SessionStore.__treestyletab__duplicateTab = SessionStore.duplicateTab;
+	SessionStore.duplicateTab = function(aWindow, aTab, aDelta = 0) {
+		aWindow.gBrowser.treeStyleTab.onBeforeTabDuplicate(aWindow, aTab, aDelta);
+		return this.__treestyletab__duplicateTab.call(this, aWindow, aTab, aDelta);
+	};
 }
diff --git a/modules/window.js b/modules/window.js
index 2760ea83..20e822a6 100644
--- a/modules/window.js
+++ b/modules/window.js
@@ -1365,11 +1365,8 @@ TreeStyleTabWindow.prototype = inherit(TreeStyleTabBase, {
 	},
 	_clickEventOnNewTabButtonHandled : false,
  
-	onBeforeTabDuplicate : function TSTWindow_onBeforeTabDuplicate(aTab, aWhere, aDelta) 
+	onBeforeTabDuplicate : function TSTWindow_onBeforeTabDuplicate(aWindow, aTab, aDelta) 
 	{
-		if (aWhere && aWhere.indexOf('tab') != 0)
-			return;
-
 		var b = this.getTabBrowserFromChild(aTab) || this.browser;
 		var behaviorPref = !aDelta ? 'autoAttach.duplicateTabCommand' :
 							aDelta < 0 ? 'autoAttach.duplicateTabCommand.back' :