diff --git a/MdePkg/Include/IndustryStandard/Acpi10.h b/MdePkg/Include/IndustryStandard/Acpi10.h
index c2f3acf75c..b463d6ff28 100644
--- a/MdePkg/Include/IndustryStandard/Acpi10.h
+++ b/MdePkg/Include/IndustryStandard/Acpi10.h
@@ -67,7 +67,7 @@ typedef struct {
 /// The commond definition of QWORD, DWORD, and WORD
 /// Address Space Descriptors
 ///
-typedef struct {
+typedef PACKED struct {
   UINT8   Desc;
   UINT16  Len;
   UINT8   ResType;