diff --git a/src/AddIns/Debugger/Debugger.AddIn/TreeModel/ArrayRangeNode.cs b/src/AddIns/Debugger/Debugger.AddIn/TreeModel/ArrayRangeNode.cs
index e341b77e218..309071608c0 100644
--- a/src/AddIns/Debugger/Debugger.AddIn/TreeModel/ArrayRangeNode.cs
+++ b/src/AddIns/Debugger/Debugger.AddIn/TreeModel/ArrayRangeNode.cs
@@ -14,7 +14,7 @@ public partial class Utils
 		public static IEnumerable<TreeNode> LazyGetChildNodesOfArray(TreeNode parent, Expression expression, ArrayDimensions dimensions)
 		{
 			if (dimensions.TotalElementCount == 0)
-				return new TreeNode[] { new TreeNode(null, "(empty)", null, null, parent, null) };
+				return new TreeNode[] { new TreeNode(null, "(empty)", null, null, parent, _ => null) };
 			
 			return new ArrayRangeNode(parent, expression, dimensions, dimensions).ChildNodes;
 		}
diff --git a/src/AddIns/Debugger/Debugger.AddIn/TreeModel/ChildNodesOfObject.cs b/src/AddIns/Debugger/Debugger.AddIn/TreeModel/ChildNodesOfObject.cs
index 2dcc2729634..7463c29caef 100644
--- a/src/AddIns/Debugger/Debugger.AddIn/TreeModel/ChildNodesOfObject.cs
+++ b/src/AddIns/Debugger/Debugger.AddIn/TreeModel/ChildNodesOfObject.cs
@@ -117,9 +117,9 @@ public static IEnumerable<TreeNode> LazyGetItemsOfIList(TreeNode parent, Express
 				error = e;
 			}
 			if (error != null) {
-				yield return new TreeNode(null, "(error)", error.Message, null, null, null);
+				yield return new TreeNode(null, "(error)", error.Message, null, null, _ => null);
 			} else if (count == 0) {
-				yield return new TreeNode(null, "(empty)", null, null, null, null);
+				yield return new TreeNode(null, "(empty)", null, null, null, _ => null);
 			} else {
 				for(int i = 0; i < count; i++) {
 					string imageName;
diff --git a/src/AddIns/Debugger/Debugger.AddIn/TreeModel/TreeNode.cs b/src/AddIns/Debugger/Debugger.AddIn/TreeModel/TreeNode.cs
index 451efe1c5a1..d00eb1df019 100644
--- a/src/AddIns/Debugger/Debugger.AddIn/TreeModel/TreeNode.cs
+++ b/src/AddIns/Debugger/Debugger.AddIn/TreeModel/TreeNode.cs
@@ -118,6 +118,8 @@ public TreeNode(TreeNode parent)
 		public TreeNode(IImage iconImage, string name, string text, string type, TreeNode parent, Func<TreeNode, IEnumerable<TreeNode>> childNodes)
 			: this(parent)
 		{
+			if (childNodes == null)
+				throw new ArgumentNullException("childNodes");
 			this.iconImage = iconImage;
 			this.name = name;
 			this.text = text;