diff --git a/MdePkg/Include/Protocol/DriverDiagnostics.h b/MdePkg/Include/Protocol/DriverDiagnostics.h
index 8acb27e52c..36a2cc2826 100644
--- a/MdePkg/Include/Protocol/DriverDiagnostics.h
+++ b/MdePkg/Include/Protocol/DriverDiagnostics.h
@@ -114,7 +114,7 @@ EFI_STATUS
 struct _EFI_DRIVER_DIAGNOSTICS_PROTOCOL {
   EFI_DRIVER_DIAGNOSTICS_RUN_DIAGNOSTICS  RunDiagnostics;
   ///
-  /// A Null-terminated ASCII string that contains one or more RFC 4646
+  /// A Null-terminated ASCII string that contains one or more ISO 639-2
   /// language codes.  This is the list of language codes that this protocol supports.  
   ///  
   CHAR8                                   *SupportedLanguages;
diff --git a/MdePkg/Include/Protocol/UnicodeCollation.h b/MdePkg/Include/Protocol/UnicodeCollation.h
index f45c9ead0e..e9eef61210 100644
--- a/MdePkg/Include/Protocol/UnicodeCollation.h
+++ b/MdePkg/Include/Protocol/UnicodeCollation.h
@@ -179,8 +179,9 @@ struct _EFI_UNICODE_COLLATION_PROTOCOL {
   EFI_UNICODE_COLLATION_STRTOFAT    StrToFat;
   
   ///
-  /// A Null-terminated ASCII string array that contains one or more 
-  /// language codes. This array is specified in RFC 4646 format.
+  /// A Null-terminated ASCII string array that contains one or more language codes.
+  /// When this field is used for UnicodeCollation2, it is specified in RFC 4646 format.
+  /// When it is used for UnicodeCollation, it is specified in ISO 639-2 format.
   ///
   CHAR8                             *SupportedLanguages;
 };