diff --git a/MdePkg/Library/BaseLib/Ia32/Thunk16.S b/MdePkg/Library/BaseLib/Ia32/Thunk16.S
index c45cdb0a2d..07d544b0c5 100644
--- a/MdePkg/Library/BaseLib/Ia32/Thunk16.S
+++ b/MdePkg/Library/BaseLib/Ia32/Thunk16.S
@@ -19,6 +19,8 @@
 #
 #------------------------------------------------------------------------------
 
+#include <Library/BaseLib.h>
+
 .globl ASM_PFX(m16Start), ASM_PFX(m16Size), ASM_PFX(mThunk16Attr), ASM_PFX(m16Gdt), ASM_PFX(m16GdtrBase), ASM_PFX(mTransition)
 .globl ASM_PFX(InternalAsmThunk16)