diff --git a/SharpTreeView/FlatListTreeNode.cs b/SharpTreeView/FlatListTreeNode.cs
index 809e81742..c20d2161e 100644
--- a/SharpTreeView/FlatListTreeNode.cs
+++ b/SharpTreeView/FlatListTreeNode.cs
@@ -33,7 +33,7 @@ namespace ICSharpCode.TreeView
 			return node != null ? node.height : 0;
 		}
 		
-		SharpTreeNode GetListRoot()
+		internal SharpTreeNode GetListRoot()
 		{
 			SharpTreeNode node = this;
 			while (node.listParent != null)
diff --git a/SharpTreeView/TreeFlattener.cs b/SharpTreeView/TreeFlattener.cs
index c35b90416..eb6895084 100644
--- a/SharpTreeView/TreeFlattener.cs
+++ b/SharpTreeView/TreeFlattener.cs
@@ -81,7 +81,7 @@ namespace ICSharpCode.TreeView
 		public int IndexOf(object item)
 		{
 			SharpTreeNode node = item as SharpTreeNode;
-			if (node != null && node.AncestorsAndSelf().Last() == root) {
+			if (node != null && node.GetListRoot() == root) {
 				if (includeRoot)
 					return SharpTreeNode.GetVisibleIndexForNode(node);
 				else