diff --git a/MdePkg/MdePkg.dec b/MdePkg/MdePkg.dec
index bda6550..598a6d0 100644
--- a/MdePkg/MdePkg.dec
+++ b/MdePkg/MdePkg.dec
@@ -2012,8 +2012,9 @@
# 1 - VT100
# 2 - VT100+
# 3 - UTF8
+ # 4 - TTYTERM, NOT defined in UEFI SPEC
# @Prompt Default Terminal Type.
- # @ValidRange 0x80000001 | 0 - 3
+ # @ValidRange 0x80000001 | 0 - 4
gEfiMdePkgTokenSpaceGuid.PcdDefaultTerminalType|0|UINT8|0x00000024
## Error level for hardware recorder.