diff --git a/MdePkg/Library/BaseLib/BaseLib.msa b/MdePkg/Library/BaseLib/BaseLib.msa
index 5cf3b550cc..b208b2cbff 100644
--- a/MdePkg/Library/BaseLib/BaseLib.msa
+++ b/MdePkg/Library/BaseLib/BaseLib.msa
@@ -175,7 +175,7 @@ WITHOUT WARRANTIES OR REPRESENTATIONS OF ANY KIND, EITHER EXPRESS OR IMPLIED.
       <Filename>Ia32/CpuPause.asm</Filename>
       <Filename>Ia32/CpuBreakpoint.asm</Filename>
       <Filename>Ia32/CpuFlushTlb.asm</Filename>
-      <Filename>Ia32/Thunk16.asm</Filename>
+      <Filename FileType="x86_asm_autogen">Ia32/Thunk16.asm</Filename>
     </Arch>
     <Arch ArchType="X64">
       <Filename>X86LowLevel.c</Filename>
@@ -267,7 +267,7 @@ WITHOUT WARRANTIES OR REPRESENTATIONS OF ANY KIND, EITHER EXPRESS OR IMPLIED.
       <Filename>X64/CpuPause.asm</Filename>
       <Filename>X64/CpuBreakpoint.asm</Filename>
       <Filename>X64/CpuFlushTlb.asm</Filename>
-      <Filename>X64/Thunk16.asm</Filename>
+      <Filename FileType="x86_asm_autogen">X64/Thunk16.asm</Filename>
     </Arch>
     <Arch ArchType="IPF">
       <Filename>Math64.c</Filename>
@@ -292,7 +292,7 @@ WITHOUT WARRANTIES OR REPRESENTATIONS OF ANY KIND, EITHER EXPRESS OR IMPLIED.
       <Filename>Ebc/Synchronization.c</Filename>
     </Arch>
   </SourceFiles>
- <Includes>
+  <Includes>
     <PackageName>MdePkg</PackageName>
   </Includes>
   <PcdCoded>
diff --git a/MdePkg/Library/BaseLib/Ia32/Thunk16.asm b/MdePkg/Library/BaseLib/Ia32/Thunk16.asm
index 454b8905bc..4d5b47017d 100644
--- a/MdePkg/Library/BaseLib/Ia32/Thunk16.asm
+++ b/MdePkg/Library/BaseLib/Ia32/Thunk16.asm
@@ -29,10 +29,6 @@ EXTERNDEF   C   m16Gdt:WORD
 EXTERNDEF   C   m16GdtrBase:WORD
 EXTERNDEF   C   mTransition:WORD
 
-THUNK_ATTRIBUTE_BIG_REAL_MODE               EQU 1
-THUNK_ATTRIBUTE_DISABLE_A20_MASK_INT_15     EQU 2
-THUNK_ATTRIBUTE_DISABLE_A20_MASK_KBD_CTRL   EQU 4
-
 IA32_REGS   STRUC   4t
 _EDI        DD      ?
 _ESI        DD      ?
diff --git a/MdePkg/Library/BaseLib/X64/Thunk16.asm b/MdePkg/Library/BaseLib/X64/Thunk16.asm
index 3121867ebb..7495ebe2c8 100644
--- a/MdePkg/Library/BaseLib/X64/Thunk16.asm
+++ b/MdePkg/Library/BaseLib/X64/Thunk16.asm
@@ -26,10 +26,6 @@ EXTERNDEF   m16Gdt:WORD
 EXTERNDEF   m16GdtrBase:WORD
 EXTERNDEF   mTransition:WORD
 
-THUNK_ATTRIBUTE_BIG_REAL_MODE               EQU 1
-THUNK_ATTRIBUTE_DISABLE_A20_MASK_INT_15     EQU 2
-THUNK_ATTRIBUTE_DISABLE_A20_MASK_KBD_CTRL   EQU 4
-
 IA32_REGS   STRUC   4t
 _EDI        DD      ?
 _ESI        DD      ?