diff --git a/content/treestyletab/res/tabsDragUtils.js b/content/treestyletab/res/tabsDragUtils.js
index 2f98ab92..b9b28464 100644
--- a/content/treestyletab/res/tabsDragUtils.js
+++ b/content/treestyletab/res/tabsDragUtils.js
@@ -13,7 +13,7 @@
    http://github.com/piroor/fxaddonlibs/blob/master/tabsDragUtils.js
 */
 (function() {
-	const currentRevision = 2;
+	const currentRevision = 3;
 
 	if (!('piro.sakura.ne.jp' in window)) window['piro.sakura.ne.jp'] = {};
 
@@ -166,6 +166,42 @@
 			return true;
 		},
 
+		getSelectedTabs : function TDU_getSelectedTabs(aEvent)
+		{
+			var b = this.getTabBrowserFromChild(aEvent.target);
+			var w = b.ownerDocument.defaultView;
+
+			var isMultipleDragEvent = this.isTabsDragging(aEvent);
+			var selectedTabs;
+			var isMultipleDrag = (
+					(
+						isMultipleDragEvent &&
+						(selectedTabs = this.getDraggedTabs(aEvent)) &&
+						selectedTabs.length
+					) ||
+					( // Firefox 4.x (https://bugzilla.mozilla.org/show_bug.cgi?id=566510)
+						'visibleTabs' in b &&
+						(selectedTabs = b.visibleTabs.filter(function(aTab) {
+							return aTab.multiselected;
+						})) &&
+						selectedTabs.length
+					) ||
+					( // Tab Utilities
+						'selectedTabs' in b &&
+						(selectedTabs = b.selectedTabs) &&
+						selectedTabs.length
+					) ||
+					( // Multiple Tab Handler
+						'MultipleTabService' in w &&
+						w.MultipleTabService.isSelected(aTab) &&
+						MultipleTabService.allowMoveMultipleTabs &&
+						(selectedTabs = w.MultipleTabService.getSelectedTabs(b)) &&
+						selectedTabs.length
+					)
+				);
+			return isMultipleDrag ? selectedTabs : [] ;
+		},
+
 		getDraggedTabs : function TDU_getDraggedTabs(aEvent)
 		{
 			var dt = aEvent.dataTransfer;
diff --git a/content/treestyletab/treestyletabbrowser.js b/content/treestyletab/treestyletabbrowser.js
index 1fd945d2..e7151511 100644
--- a/content/treestyletab/treestyletabbrowser.js
+++ b/content/treestyletab/treestyletabbrowser.js
@@ -3676,22 +3676,8 @@ TreeStyleTabBrowser.prototype = {
 
 		var sourceWindow = aTab.ownerDocument.defaultView;
 		var sourceBrowser = this.getTabBrowserFromChild(aTab);
-
-		var dt = aInfo.event && aInfo.event.dataTransfer;
-		var isMultipleDragEvent = window['piro.sakura.ne.jp'].tabsDragUtils.isTabsDragging(aInfo.event);
-		var isMultipleMove = (
-				isMultipleDragEvent ||
-				(
-					'MultipleTabService' in sourceWindow &&
-					sourceWindow.MultipleTabService.isSelected(aTab) &&
-					MultipleTabService.allowMoveMultipleTabs
-				)
-			);
-
-		if (isMultipleMove) {
-			draggedTabs = isMultipleDragEvent ?
-							window['piro.sakura.ne.jp'].tabsDragUtils.getDraggedTabs(aInfo.event) :
-							sourceWindow.MultipleTabService.getSelectedTabs(sourceBrowser);
+		var draggedTabs = window['piro.sakura.ne.jp'].tabsDragUtils.getSelectedTabs(aInfo.event);
+		if (draggedTabs.length > 1) {
 			if (!(aInfo.action & this.kACTIONS_FOR_DESTINATION)) {
 				draggedRoots = [];
 				draggedTabs.forEach(function(aTab) {