diff --git a/MdePkg/Library/BaseRngLib/BaseRngLibInternals.h b/MdePkg/Library/BaseRngLib/BaseRngLibInternals.h
index a9cbce1530..d0abcc3452 100644
--- a/MdePkg/Library/BaseRngLib/BaseRngLibInternals.h
+++ b/MdePkg/Library/BaseRngLib/BaseRngLibInternals.h
@@ -9,6 +9,7 @@ SPDX-License-Identifier: BSD-2-Clause-Patent
 **/
 
 #ifndef BASE_RNGLIB_INTERNALS_H_
+#define BASE_RNGLIB_INTERNALS_H_
 
 /**
   Generates a 16-bit random number.