diff --git a/MdePkg/Library/BaseUefiDecompressLib/BaseUefiDecompressLib.c b/MdePkg/Library/BaseUefiDecompressLib/BaseUefiDecompressLib.c
index 15c3325cd4..e59a9de3d1 100644
--- a/MdePkg/Library/BaseUefiDecompressLib/BaseUefiDecompressLib.c
+++ b/MdePkg/Library/BaseUefiDecompressLib/BaseUefiDecompressLib.c
@@ -1,7 +1,7 @@
 /** @file
   UEFI Decompress Library implementation refer to UEFI specification.
 
-  Copyright (c) 2006 - 2010, Intel Corporation. All rights reserved.<BR>
+  Copyright (c) 2006 - 2014, Intel Corporation. All rights reserved.<BR>
   Portions copyright (c) 2008 - 2009, Apple Inc. All rights reserved.<BR>
   This program and the accompanying materials
   are licensed and made available under the terms and conditions of the BSD License
@@ -333,6 +333,7 @@ ReadPTLen (
   UINT16  Index;
   UINT32  Mask;
 
+  ASSERT (nn <= NPT);
   //
   // Read Extra Set Code Length Array size 
   //