diff --git a/MdeModulePkg/Include/Library/NetLib.h b/MdeModulePkg/Include/Library/NetLib.h
index 875af7b283..fa59254a25 100644
--- a/MdeModulePkg/Include/Library/NetLib.h
+++ b/MdeModulePkg/Include/Library/NetLib.h
@@ -2,7 +2,7 @@
   This library is only intended to be used by UEFI network stack modules.
   It provides basic functions for the UEFI network stack.
 
-Copyright (c) 2005 - 2011, Intel Corporation. All rights reserved.<BR>
+Copyright (c) 2005 - 2012, Intel Corporation. All rights reserved.<BR>
 This program and the accompanying materials
 are licensed and made available under the terms and conditions of the BSD License
 which accompanies this distribution.  The full text of the license may be found at<BR>
@@ -1087,7 +1087,8 @@ NetLibGetMacAddress (
   @param[in]   ServiceHandle         The handle where network service binding protocol is
                                      installed.
   @param[in]   ImageHandle           The image handle used to act as the agent handle to
-                                     get the simple network protocol.
+                                     get the simple network protocol. This parameter is
+                                     optional and may be NULL.
   @param[out]  MacString             The pointer to store the address of the string
                                      representation of  the mac address.
 
@@ -1100,7 +1101,7 @@ EFI_STATUS
 EFIAPI
 NetLibGetMacString (
   IN  EFI_HANDLE            ServiceHandle,
-  IN  EFI_HANDLE            ImageHandle,
+  IN  EFI_HANDLE            ImageHandle, OPTIONAL
   OUT CHAR16                **MacString
   );
 
diff --git a/MdeModulePkg/Library/DxeNetLib/DxeNetLib.c b/MdeModulePkg/Library/DxeNetLib/DxeNetLib.c
index 1743e9bdfa..f74dcdaeae 100644
--- a/MdeModulePkg/Library/DxeNetLib/DxeNetLib.c
+++ b/MdeModulePkg/Library/DxeNetLib/DxeNetLib.c
@@ -1,7 +1,7 @@
 /** @file
   Network library.
 
-Copyright (c) 2005 - 2011, Intel Corporation. All rights reserved.<BR>
+Copyright (c) 2005 - 2012, Intel Corporation. All rights reserved.<BR>
 This program and the accompanying materials
 are licensed and made available under the terms and conditions of the BSD License
 which accompanies this distribution.  The full text of the license may be found at
@@ -2168,7 +2168,8 @@ NetLibGetMacAddress (
   @param[in]   ServiceHandle         The handle where network service binding protocol is
                                      installed on.
   @param[in]   ImageHandle           The image handle used to act as the agent handle to
-                                     get the simple network protocol.
+                                     get the simple network protocol. This parameter is
+                                     optional and may be NULL.
   @param[out]  MacString             The pointer to store the address of the string
                                      representation of  the mac address.
 
@@ -2181,7 +2182,7 @@ EFI_STATUS
 EFIAPI
 NetLibGetMacString (
   IN  EFI_HANDLE            ServiceHandle,
-  IN  EFI_HANDLE            ImageHandle,
+  IN  EFI_HANDLE            ImageHandle, OPTIONAL
   OUT CHAR16                **MacString
   )
 {