diff --git a/chrome/content/zotero/xpcom/itemTreeView.js b/chrome/content/zotero/xpcom/itemTreeView.js
index a312e5fa4a..5a3c5f10af 100644
--- a/chrome/content/zotero/xpcom/itemTreeView.js
+++ b/chrome/content/zotero/xpcom/itemTreeView.js
@@ -2054,7 +2054,7 @@ Zotero.ItemTreeView.prototype.onDragStart = function (event) {
 	}
 	
 	// Get Quick Copy format for current URL
-	var url = this._ownerDocument.defaultView.content ?
+	var url = this._ownerDocument.defaultView.content && this._ownerDocument.defaultView.content.location ?
 				this._ownerDocument.defaultView.content.location.href : null;
 	var format = Zotero.QuickCopy.getFormatFromURL(url);