diff --git a/content/treestyletab/group.js b/content/treestyletab/group.js
index 7a15c597..af160942 100644
--- a/content/treestyletab/group.js
+++ b/content/treestyletab/group.js
@@ -147,14 +147,47 @@ function getTabById(aId)
 
 function onItemClick(aEvent)
 {
+	var gBrowser = getOwnerTabBrowser();
+	if (!gBrowser)
+		return;
+
 	var tab = getTabById(aEvent.getData('id'));
-	if (tab)
+	if (!tab)
+		return;
+
+	var button = aEvent.getData('button');
+	var altKey = aEvent.getData('altKey');
+	var ctrlKey = aEvent.getData('ctrlKey');
+	var metaKey = aEvent.getData('metaKey');
+	var shiftKey = aEvent.getData('shiftKey');
+	var isMiddleClick = (
+			(
+				button == 1 &&
+				!altKey &&
+				!ctrlKey &&
+				!metaKey &&
+				!shiftKey
+			) ||
+			(
+				button == 0 &&
+				!altKey &&
+				(ctrlKey || metaKey) &&
+				!shiftKey
+			)
+		);
+
+	if (isMiddleClick)
+		gBrowser.removeTab(tab);
+	else if (button != 2)
 		gBrowser.selectedTab = tab;
 }
 
 
 function updateTree()
 {
+	if (window.closed)
+		return;
+
 	var tree = document.getElementById('tree');
 
 	var range = document.createRange();
@@ -162,13 +195,18 @@ function updateTree()
 	range.deleteContents();
 	range.detach();
 
-	tree.appendChild(PseudoTreeBuilder.build(getOwnerTab()));
+	var contents = PseudoTreeBuilder.build(getOwnerTab());
+	if (contents)
+		tree.appendChild(contents);
 }
 
 function checkUpdateTreeNow()
 {
 	if (getOwnerTab().selected)
-		window.setTimeout(onTabSelect, 0);
+		window.setTimeout(function() {
+			if (!window.closed)
+				onTabSelect();
+		}, 0);
 }
 
 var gShouldUpdate = false;
diff --git a/modules/pseudoTreeBuilder.js b/modules/pseudoTreeBuilder.js
index cd7fc33a..442aa924 100644
--- a/modules/pseudoTreeBuilder.js
+++ b/modules/pseudoTreeBuilder.js
@@ -58,8 +58,11 @@ var PseudoTreeBuilder = {
 
 		var tree = this.createTabItem(aTab);
 
-		tree.querySelector("."+this.kTREEROW)
-			.className += " "+this.kROOTITEM;
+		var row = tree.querySelector("."+this.kTREEROW);
+		if (!row)
+			return;
+
+		row.className += " "+this.kROOTITEM;
 
 		tree.setAttribute('onclick', <![CDATA[
 			var doc = event.target.ownerDocument;
@@ -74,6 +77,11 @@ var PseudoTreeBuilder = {
 				var customEvent = doc.createEvent('DataContainerEvent');
 				customEvent.initEvent(%EVENT_TYPE%, true, true);
 				customEvent.setData('id', label.getAttribute('tab-id'));
+				customEvent.setData('button', event.button);
+				customEvent.setData('altKey', event.altKey);
+				customEvent.setData('ctrlKey', event.ctrlKey);
+				customEvent.setData('metaKey', event.metaKey);
+				customEvent.setData('shiftKey', event.shiftKey);
 				event.target.dispatchEvent(customEvent);
 			}
 		]]>.toString().replace('%EVENT_TYPE%', this.kTAB_LINK_CLICK.quote()));