diff --git a/ShellPkg/Library/UefiShellAcpiViewCommandLib/AcpiParser.h b/ShellPkg/Library/UefiShellAcpiViewCommandLib/AcpiParser.h
index 0b7726b..5e34a70 100644
--- a/ShellPkg/Library/UefiShellAcpiViewCommandLib/AcpiParser.h
+++ b/ShellPkg/Library/UefiShellAcpiViewCommandLib/AcpiParser.h
@@ -283,7 +283,9 @@
   FNPTR_PRINT_FORMATTER PrintFormatter;
 
   /// Optional pointer which may be set to request the parser to update
-  /// a pointer to the field data. If unused this must be set to NULL.
+  /// a pointer to the field data. This value is set after the FieldValidator
+  /// has been called and therefore should not be used by the FieldValidator.
+  /// If unused this must be set to NULL.
   VOID**                ItemPtr;
 
   /// Optional pointer to a field validator function.