diff --git a/ICSharpCode.ILSpyX/TreeView/SharpTreeNodeCollection.cs b/ICSharpCode.ILSpyX/TreeView/SharpTreeNodeCollection.cs
index 8b69a9553d..d724285763 100644
--- a/ICSharpCode.ILSpyX/TreeView/SharpTreeNodeCollection.cs
+++ b/ICSharpCode.ILSpyX/TreeView/SharpTreeNodeCollection.cs
@@ -73,7 +73,10 @@ void ThrowIfValueIsNullOrHasParent(SharpTreeNode node)
 
 		public SharpTreeNode this[int index] {
 			get {
-				return list[index];
+				if (index >= 0 && index < list.Count)
+					return list[index];
+				else
+					return null;
 			}
 			set {
 				ThrowOnReentrancy();
diff --git a/ILSpy/Controls/TreeView/SharpTreeView.cs b/ILSpy/Controls/TreeView/SharpTreeView.cs
index faa7cb2f05..ab86539bd9 100644
--- a/ILSpy/Controls/TreeView/SharpTreeView.cs
+++ b/ILSpy/Controls/TreeView/SharpTreeView.cs
@@ -561,8 +561,12 @@ List<DropTarget> BuildDropTargets(SharpTreeViewItem item, DragEventArgs e)
 			{
 				if (node.IsExpanded && node.Children.Count > 0)
 				{
-					var firstChildItem = ItemContainerGenerator.ContainerFromItem(node.Children[0]) as SharpTreeViewItem;
-					TryAddDropTarget(result, firstChildItem, DropPlace.Before, e);
+					var nodeChild = node.Children[0];
+					if (nodeChild != null)
+					{
+						var firstChildItem = ItemContainerGenerator.ContainerFromItem(node.Children[0]) as SharpTreeViewItem;
+						TryAddDropTarget(result, firstChildItem, DropPlace.Before, e);
+					}
 				}
 				else
 				{