diff --git a/content/treestyletab/res/tabsDragUtils.js b/content/treestyletab/res/tabsDragUtils.js
index 652c7f3d..d4e6c29f 100644
--- a/content/treestyletab/res/tabsDragUtils.js
+++ b/content/treestyletab/res/tabsDragUtils.js
@@ -410,7 +410,13 @@
 		collectAlignedTabs : function TDU_collectAlignedTabs(tabs, context)
 		{
 			context.allAnimatedTabs = tabs;
-			var base = context.draggedTab.boxObject[context.align];
+			var baseTab = context.draggedTab;
+			if (!baseTab.pinned)
+				return tabs;
+
+			// With Tree Style Tabs, pinned tabs are shown with multiple rows.
+			// We should animate only tabs in the same row.
+			var base = baseTab.boxObject[context.align];
 			return tabs.filter(function(aTab) {
 				return aTab.boxObject[context.align] == base;
 			});
diff --git a/modules/tabbarDNDObserver.js b/modules/tabbarDNDObserver.js
index 6c620cf9..c54d94c3 100644
--- a/modules/tabbarDNDObserver.js
+++ b/modules/tabbarDNDObserver.js
@@ -268,11 +268,16 @@ catch(e) {
 
 		let draggedTab = aEvent.dataTransfer && aEvent.dataTransfer.mozGetDataAt(TAB_DROP_TYPE, 0);
 		if (draggedTab._dragData) {
-			let tabs = sv.getTabs(b).filter(function(aTab) { 
-					return !aTab._dragData;
+			let sameTypeUndraggedTabs = tabs.filter(function(aTab) { 
+					return !aTab._dragData && aTab.pinned == draggedTab.pinned;
 				});
-			tab = sv.getTabFromCoordinates(aEvent, tabs) ||
-					sv.getTabFromCoordinates(aEvent);
+			tab = draggedTab.pinned ?
+					// pinned tabs cannot be dropped to another pinned tab, so
+					// we can use the drop position calculated by "_animateTabMove()".
+					tabs[draggedTab._dragData.animDropIndex] :
+					// otherwise, we have to find "drop target" tab from screen coordinates.
+					sv.getTabFromCoordinates(aEvent, sameTypeUndraggedTabs) ||
+						sv.getTabFromCoordinates(aEvent);
 		}
 
 		var isTabMoveFromOtherWindow = aSourceTab && aSourceTab.ownerDocument != d;