diff --git a/MdePkg/MdePkg.dec b/MdePkg/MdePkg.dec
index bda6550ed6..598a6d07f4 100644
--- a/MdePkg/MdePkg.dec
+++ b/MdePkg/MdePkg.dec
@@ -2012,8 +2012,9 @@
   #  1 - VT100<BR>
   #  2 - VT100+<BR>
   #  3 - UTF8<BR>
+  #  4 - TTYTERM, NOT defined in UEFI SPEC<BR>
   # @Prompt Default Terminal Type.
-  # @ValidRange 0x80000001 | 0 - 3
+  # @ValidRange 0x80000001 | 0 - 4
   gEfiMdePkgTokenSpaceGuid.PcdDefaultTerminalType|0|UINT8|0x00000024
 
   ## Error level for hardware recorder.