diff --git a/src/System.Management.Automation/engine/parser/PreOrderVisitor.cs b/src/System.Management.Automation/engine/parser/PreOrderVisitor.cs
index 0bf5368fddb..33b2fadec64 100644
--- a/src/System.Management.Automation/engine/parser/PreOrderVisitor.cs
+++ b/src/System.Management.Automation/engine/parser/PreOrderVisitor.cs
@@ -254,6 +254,7 @@ public abstract class AstVisitor2 : AstVisitor
     /// Implement this interface when you implement <see cref="AstVisitor"/> or <see cref="AstVisitor2"/> when
     /// you want to do something after possibly visiting the children of the ast.
     /// </summary>
+#nullable enable
     public interface IAstPostVisitHandler
     {
         /// <summary>