diff --git a/CryptoPkg/Library/Include/CrtLibSupport.h b/CryptoPkg/Library/Include/CrtLibSupport.h
index 94b0e6b601..f36fe08f0c 100644
--- a/CryptoPkg/Library/Include/CrtLibSupport.h
+++ b/CryptoPkg/Library/Include/CrtLibSupport.h
@@ -87,6 +87,7 @@ SPDX-License-Identifier: BSD-2-Clause-Patent
 #define UINT_MAX      0xFFFFFFFF      /* Maximum unsigned int value */
 #define ULONG_MAX     0xFFFFFFFF      /* Maximum unsigned long value */
 #define CHAR_BIT      8               /* Number of bits in a char */
+#define SIZE_MAX      0xFFFFFFFF      /* Maximum unsigned size_t */
 
 //
 // Address families.