diff --git a/src/Avalonia.Controls.TreeDataGrid/Primitives/RealizedStackElements.cs b/src/Avalonia.Controls.TreeDataGrid/Primitives/RealizedStackElements.cs
index 47f24cc4..b03623cc 100644
--- a/src/Avalonia.Controls.TreeDataGrid/Primitives/RealizedStackElements.cs
+++ b/src/Avalonia.Controls.TreeDataGrid/Primitives/RealizedStackElements.cs
@@ -294,6 +294,7 @@ public void ItemsInserted(int index, int count, Action<Control, int, int> update
                 {
                     // The insertion point was before the first element, update the first index.
                     _firstIndex += count;
+                    _startUUnstable = true;
                 }
                 else
                 {