diff --git a/MdePkg/Include/Library/BaseLib.h b/MdePkg/Include/Library/BaseLib.h
index 5d7067ee85..728e89d2bf 100644
--- a/MdePkg/Include/Library/BaseLib.h
+++ b/MdePkg/Include/Library/BaseLib.h
@@ -4599,6 +4599,11 @@ CalculateCrc16Ansi (
   IN  UINT16      InitialValue
   );
 
+//
+// Initial value for the CRC16-ANSI algorithm, when no prior checksum has been calculated.
+//
+#define CRC16ANSI_INIT  0xffff
+
 /**
    Calculates the CRC32c checksum of the given buffer.
 
diff --git a/MdePkg/Library/BaseLib/CheckSum.c b/MdePkg/Library/BaseLib/CheckSum.c
index b6a0765731..57d324c82b 100644
--- a/MdePkg/Library/BaseLib/CheckSum.c
+++ b/MdePkg/Library/BaseLib/CheckSum.c
@@ -678,13 +678,13 @@ CalculateCrc16Ansi (
 
   Buf = Buffer;
 
-  Crc = ~InitialValue;
+  Crc = InitialValue;
 
   while (Length-- != 0) {
     Crc = mCrc16LookupTable[(Crc & 0xFF) ^ *(Buf++)] ^ (Crc >> 8);
   }
 
-  return ~Crc;
+  return Crc;
 }
 
 GLOBAL_REMOVE_IF_UNREFERENCED STATIC CONST UINT32  mCrc32cLookupTable[256] = {