diff --git a/MdePkg/Include/IndustryStandard/Acpi50.h b/MdePkg/Include/IndustryStandard/Acpi50.h
index 067ab68c3..50d277591 100644
--- a/MdePkg/Include/IndustryStandard/Acpi50.h
+++ b/MdePkg/Include/IndustryStandard/Acpi50.h
@@ -995,9 +995,9 @@ typedef struct {
 ///
 /// Memory Aggregator Device Type
 ///
-#define EFI_ACPI_5_0_PMMT_MEMORY_AGGREGATOR_DEVICE_TYPE_SOCKET            0x1
-#define EFI_ACPI_5_0_PMMT_MEMORY_AGGREGATOR_DEVICE_TYPE_MEMORY_CONTROLLER 0x2
-#define EFI_ACPI_5_0_PMMT_MEMORY_AGGREGATOR_DEVICE_TYPE_DIMM              0x3
+#define EFI_ACPI_5_0_PMMT_MEMORY_AGGREGATOR_DEVICE_TYPE_SOCKET            0x0
+#define EFI_ACPI_5_0_PMMT_MEMORY_AGGREGATOR_DEVICE_TYPE_MEMORY_CONTROLLER 0x1
+#define EFI_ACPI_5_0_PMMT_MEMORY_AGGREGATOR_DEVICE_TYPE_DIMM              0x2
 
 ///
 /// Socket Memory Aggregator Device Structure.