diff --git a/src/Avalonia.Controls.TreeDataGrid/Selection/TreeSelectedItems.cs b/src/Avalonia.Controls.TreeDataGrid/Selection/TreeSelectedItems.cs
index 19494388..ee25a7b3 100644
--- a/src/Avalonia.Controls.TreeDataGrid/Selection/TreeSelectedItems.cs
+++ b/src/Avalonia.Controls.TreeDataGrid/Selection/TreeSelectedItems.cs
@@ -56,7 +56,8 @@ public T? this[int index]
             {
                 for (var i = range.Begin; i <= range.End; ++i)
                 {
-                    yield return node.ItemsView![i];
+                    if (node.ItemsView is not null)
+                        yield return node.ItemsView[i];
                 }
             }
 
@@ -110,4 +111,4 @@ public TreeSelectedItems(TreeSelectionModelBase<T> root) : base(root) { }
                 yield return i;
         }
     }
-}
\ No newline at end of file
+}