diff --git a/content/treestyletab/treestyletab.js b/content/treestyletab/treestyletab.js
index 89f32aa4..62acee0b 100644
--- a/content/treestyletab/treestyletab.js
+++ b/content/treestyletab/treestyletab.js
@@ -1125,20 +1125,6 @@ catch(e) {
 			)
 		);
 
-		if (window.contentAreaDNDObserver &&
-			!('getSupportedFlavours' in contentAreaDNDObserver)) { // Firefox 3.6 or later
-			eval('contentAreaDNDObserver.onDrop = '+
-				contentAreaDNDObserver.onDrop.toSource().replace(
-					'var types = aEvent.dataTransfer.types;',
-					<![CDATA[$&
-						if (gBrowser.treeStyleTab.panelDNDObserver.canDrop(aEvent, gBrowser.treeStyleTab.getCurrentDragSession())) {
-							return gBrowser.treeStyleTab.panelDNDObserver.onDrop(aEvent, null, gBrowser.treeStyleTab.getCurrentDragSession());
-						}
-					]]>
-				)
-			);
-		}
-
 		if ('PrintUtils' in window) {
 			eval('PrintUtils.printPreview = '+PrintUtils.printPreview.toSource().replace(
 				'{',
diff --git a/content/treestyletab/treestyletabbrowser.js b/content/treestyletab/treestyletabbrowser.js
index 7f38d2c2..9c7bcabf 100644
--- a/content/treestyletab/treestyletabbrowser.js
+++ b/content/treestyletab/treestyletabbrowser.js
@@ -230,7 +230,8 @@ TreeStyleTabBrowser.prototype = {
 		strip.addEventListener('click',     this, true);
 		b.mPanelContainer.addEventListener('dragexit', this, false);
 		b.mPanelContainer.addEventListener('dragover', this, false);
-		b.mPanelContainer.addEventListener('dragdrop', this, false);
+		b.mPanelContainer.addEventListener('drop',     this, true);
+		b.mPanelContainer.addEventListener('dragdrop', this, false); // for Firefox 3.5 or older
 
 		if (this.isFloating)
 			window.addEventListener('resize', this, true);
@@ -1344,7 +1345,8 @@ TreeStyleTabBrowser.prototype = {
 		strip.removeEventListener('click',     this, true);
 		b.mPanelContainer.removeEventListener('dragexit', this, false);
 		b.mPanelContainer.removeEventListener('dragover', this, false);
-		b.mPanelContainer.removeEventListener('dragdrop', this, false);
+		b.mPanelContainer.removeEventListener('drop',     this, true);
+		b.mPanelContainer.removeEventListener('dragdrop', this, false); // for Firefox 3.5 or older
 
 		if (this.isFloating)
 			window.removeEventListener('resize', this, true);
@@ -1647,7 +1649,7 @@ TreeStyleTabBrowser.prototype = {
 						observer = this.tabbarDNDObserver;
 						canDrop = true;
 					}
-					else {
+					else { // for Firefox 3.5 or older
 						observer = this.panelDNDObserver;
 						canDrop = observer.canDrop(aEvent, this.getCurrentDragSession());
 					}
@@ -1658,6 +1660,17 @@ TreeStyleTabBrowser.prototype = {
 				}
 				return;
 
+			// drop on panelContainer
+			case 'drop':
+				let (session = this.getCurrentDragSession()) {
+					if (this.panelDNDObserver.canDrop(aEvent, session)) {
+						this.panelDNDObserver.onDrop(aEvent, null, session);
+						aEvent.preventDefault();
+						aEvent.stopPropagation();
+					}
+				}
+				return;
+
 
 			case 'mouseover':
 				if (this.isEventFiredOnTwisty(aEvent))