diff --git a/MdePkg/Library/BaseLib/String.c b/MdePkg/Library/BaseLib/String.c
index 25962f85b2..fa96d1c1ee 100644
--- a/MdePkg/Library/BaseLib/String.c
+++ b/MdePkg/Library/BaseLib/String.c
@@ -1,7 +1,7 @@
 /** @file
   Unicode and ASCII string primitives.
 
-  Copyright (c) 2006 - 2014, Intel Corporation. All rights reserved.<BR>
+  Copyright (c) 2006 - 2016, 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
@@ -315,6 +315,7 @@ StrnCmp (
   }
 
   while ((*FirstString != L'\0') &&
+         (*SecondString != L'\0') &&
          (*FirstString == *SecondString) &&
          (Length > 1)) {
     FirstString++;
@@ -1474,6 +1475,7 @@ AsciiStrnCmp (
   }
 
   while ((*FirstString != '\0') &&
+         (*SecondString != '\0') &&
          (*FirstString == *SecondString) &&
          (Length > 1)) {
     FirstString++;