diff --git a/PInvoke/Shell32/ShlObj.cs b/PInvoke/Shell32/ShlObj.cs
index 98bda05c..373cdd8a 100644
--- a/PInvoke/Shell32/ShlObj.cs
+++ b/PInvoke/Shell32/ShlObj.cs
@@ -3879,11 +3879,11 @@ namespace Vanara.PInvoke
 		/// values contained in the dwItem1 and dwItem2 parameters must be the same, respectively, for all specified events.
 		/// </param>
 		/// <param name="uFlags">Flags that, when combined bitwise with SHCNF_TYPE, indicate the meaning of the dwItem1 and dwItem2 parameters.</param>
-		/// <param name="dwItem1">Optional. First event-dependent value.</param>
-		/// <param name="dwItem2">Optional. Second event-dependent value.</param>
+		/// <param name="dwItem1">Optional. First event-dependent value or <see cref="PIDL.Null"/>.</param>
+		/// <param name="dwItem2">Optional. Second event-dependent value or <see cref="PIDL.Null"/>.</param>
 		[DllImport(Lib.Shell32, ExactSpelling = true)]
 		[PInvokeData("Shlobj.h")]
-		public static extern void SHChangeNotify(SHCNE wEventId, SHCNF uFlags, PIDL dwItem1, [Optional] PIDL dwItem2);
+		public static extern void SHChangeNotify(SHCNE wEventId, SHCNF uFlags, PIDL dwItem1, PIDL dwItem2);
 
 		/// <summary>
 		/// <para>Unregisters the client's window process from receiving SHChangeNotify messages.</para>