diff --git a/chrome/content/zotero/xpcom/itemTreeView.js b/chrome/content/zotero/xpcom/itemTreeView.js
index 7f7b3faf7..6b0c8de16 100644
--- a/chrome/content/zotero/xpcom/itemTreeView.js
+++ b/chrome/content/zotero/xpcom/itemTreeView.js
@@ -2896,7 +2896,7 @@ Zotero.ItemTreeView.prototype.canDropCheck = function (row, orient, dataTransfer
 	
 	var itemGroup = this._itemGroup;
 	
-	if (orient == 0) {
+	if (row != -1 && orient == 0) {
 		var rowItem = this._getItemAtRow(row).ref; // the item we are dragging over
 	}
 	
@@ -2904,7 +2904,7 @@ Zotero.ItemTreeView.prototype.canDropCheck = function (row, orient, dataTransfer
 		var items = Zotero.Items.get(ids);
 		
 		// Directly on a row
-		if (orient == 0) {
+		if (rowItem) {
 			var canDrop = false;
 			
 			for each(var item in items) {
@@ -2981,7 +2981,7 @@ Zotero.ItemTreeView.prototype.canDropCheck = function (row, orient, dataTransfer
 	}
 	else if (dataType == "text/x-moz-url" || dataType == 'application/x-moz-file') {
 		// Disallow direct drop on a non-regular item (e.g. note)
-		if (orient == 0) {
+		if (rowItem) {
 			if (!rowItem.isRegularItem()) {
 				return false;
 			}