diff --git a/src/System.Management.Automation/engine/parser/ast.cs b/src/System.Management.Automation/engine/parser/ast.cs
index 79d8fcc537..ecfd5d4eab 100644
--- a/src/System.Management.Automation/engine/parser/ast.cs
+++ b/src/System.Management.Automation/engine/parser/ast.cs
@@ -8139,6 +8139,7 @@ namespace System.Management.Automation.Language
     /// <summary>
     /// The name and attributes of a type.
     /// </summary>
+#nullable enable
     public interface ITypeName
     {
         /// <summary>
@@ -8154,7 +8155,7 @@ namespace System.Management.Automation.Language
         /// <summary>
         /// The name of the assembly, if specified, otherwise null.
         /// </summary>
-        string AssemblyName { get; }
+        string? AssemblyName { get; }
 
         /// <summary>
         /// Returns true if the type names an array, false otherwise.
@@ -8169,20 +8170,21 @@ namespace System.Management.Automation.Language
         /// <summary>
         /// Returns the <see cref="System.Type"/> that this typename represents, if such a type exists, null otherwise.
         /// </summary>
-        Type GetReflectionType();
+        Type? GetReflectionType();
 
         /// <summary>
         /// Assuming the typename is an attribute, returns the <see cref="System.Type"/> that this typename represents.
         /// By convention, the typename may omit the suffix "Attribute".  Lookup will attempt to resolve the type as is,
         /// and if that fails, the suffix "Attribute" will be appended.
         /// </summary>
-        Type GetReflectionAttributeType();
+        Type? GetReflectionAttributeType();
 
         /// <summary>
         /// The extent of the typename.
         /// </summary>
         IScriptExtent Extent { get; }
     }
+#nullable restore
 
 #nullable enable
     internal interface ISupportsTypeCaching