diff --git a/sdk/xtdk/xtcommon.h b/sdk/xtdk/xtcommon.h
index 41d4b11..3ce88fe 100644
--- a/sdk/xtdk/xtcommon.h
+++ b/sdk/xtdk/xtcommon.h
@@ -13,6 +13,15 @@
 #include "xtstruct.h"
 
 
+/* 128-bit buffer containing a unique identifier value */
+typedef struct _GUID
+{
+    UINT Data1;
+    USHORT Data2;
+    USHORT Data3;
+    UCHAR Data4[8];
+} GUID, *PGUID;
+
 /* Double linked list structure definition */
 typedef struct _LIST_ENTRY
 {
diff --git a/sdk/xtdk/xtstruct.h b/sdk/xtdk/xtstruct.h
index f4c9dfe..7c0e474 100644
--- a/sdk/xtdk/xtstruct.h
+++ b/sdk/xtdk/xtstruct.h
@@ -142,6 +142,7 @@ typedef struct _EFI_USB_DEVICE_PATH EFI_USB_DEVICE_PATH, *PEFI_USB_DEVICE_PATH;
 typedef struct _EFI_USB_WWID_DEVICE_PATH EFI_USB_WWID_DEVICE_PATH, *PEFI_USB_WWID_DEVICE_PATH;
 typedef struct _EFI_VENDOR_DEVICE_PATH EFI_VENDOR_DEVICE_PATH, *PEFI_VENDOR_DEVICE_PATH;
 typedef struct _EFI_VLAN_DEVICE_PATH EFI_VLAN_DEVICE_PATH, *PEFI_VLAN_DEVICE_PATH;
+typedef struct _GUID GUID, *PGUID;
 typedef struct _LIST_ENTRY LIST_ENTRY, *PLIST_ENTRY;
 typedef struct _LIST_ENTRY32 LIST_ENTRY32, *PLIST_ENTRY32;
 typedef struct _LIST_ENTRY64 LIST_ENTRY64, *PLIST_ENTRY64;