diff --git a/content/treestyletab/res/tabsDragUtils.js b/content/treestyletab/res/tabsDragUtils.js
index b9b28464..1b0d3b25 100644
--- a/content/treestyletab/res/tabsDragUtils.js
+++ b/content/treestyletab/res/tabsDragUtils.js
@@ -148,7 +148,9 @@
 					'ancestor-or-self::*[local-name()="tabbrowser"] | '+
 					'ancestor-or-self::*[local-name()="tabs" and @tabbrowser]',
 					aTabBrowserChild,
-					XPathResult.FIRST_ORDERED_NODE_TYPE
+					null,
+					XPathResult.FIRST_ORDERED_NODE_TYPE,
+					null
 				).singleNodeValue;
 			return (b && b.tabbrowser) || b;
 		},
@@ -166,17 +168,17 @@
 			return true;
 		},
 
-		getSelectedTabs : function TDU_getSelectedTabs(aEvent)
+		getSelectedTabs : function TDU_getSelectedTabs(aEventOrTabBrowser)
 		{
-			var b = this.getTabBrowserFromChild(aEvent.target);
+			var event = aEventOrTabBrowser instanceof Components.interfaces.nsIDOMEvent ? aEventOrTabBrowser : null ;
+			var b = this.getTabBrowserFromChild(event ? event.target : aEventOrTabBrowser );
 			var w = b.ownerDocument.defaultView;
 
-			var isMultipleDragEvent = this.isTabsDragging(aEvent);
 			var selectedTabs;
 			var isMultipleDrag = (
 					(
-						isMultipleDragEvent &&
-						(selectedTabs = this.getDraggedTabs(aEvent)) &&
+						this.isTabsDragging(event) &&
+						(selectedTabs = this.getDraggedTabs(event)) &&
 						selectedTabs.length
 					) ||
 					( // Firefox 4.x (https://bugzilla.mozilla.org/show_bug.cgi?id=566510)
diff --git a/content/treestyletab/treestyletabbrowser.js b/content/treestyletab/treestyletabbrowser.js
index e7151511..74acf466 100644
--- a/content/treestyletab/treestyletabbrowser.js
+++ b/content/treestyletab/treestyletabbrowser.js
@@ -3671,13 +3671,15 @@ TreeStyleTabBrowser.prototype = {
 		var targetBrowser = this.mTabBrowser;
 		var tabs = this.getTabsArray(targetBrowser);
 
-		var draggedTabs = [aTab];
-		var draggedRoots = [aTab];
-
 		var sourceWindow = aTab.ownerDocument.defaultView;
 		var sourceBrowser = this.getTabBrowserFromChild(aTab);
-		var draggedTabs = window['piro.sakura.ne.jp'].tabsDragUtils.getSelectedTabs(aInfo.event);
+
+		var draggedTabs = window['piro.sakura.ne.jp'].tabsDragUtils.getSelectedTabs(aInfo.event || sourceBrowser);
+		var draggedRoots = [aTab];
+		var isMultipleMove = false;
+
 		if (draggedTabs.length > 1) {
+			isMultipleMove = true;
 			if (!(aInfo.action & this.kACTIONS_FOR_DESTINATION)) {
 				draggedRoots = [];
 				draggedTabs.forEach(function(aTab) {
@@ -3695,7 +3697,7 @@ TreeStyleTabBrowser.prototype = {
 			}
 		}
 		else if (aInfo.action & this.kACTIONS_FOR_DESTINATION) {
-			draggedTabs = draggedTabs.concat(sourceBrowser.treeStyleTab.getDescendantTabs(aTab));
+			draggedTabs = [aTab].concat(sourceBrowser.treeStyleTab.getDescendantTabs(aTab));
 		}
 
 		return {