diff --git a/sdk/xtdk/xtbase.h b/sdk/xtdk/xtbase.h
index d1a2f11..2ba6a54 100644
--- a/sdk/xtdk/xtbase.h
+++ b/sdk/xtdk/xtbase.h
@@ -50,6 +50,28 @@ typedef struct _LIST_ENTRY64
     ULONGLONG Blink;
 } LIST_ENTRY64, *PLIST_ENTRY64;
 
+/* Single linked list structure definition */
+typedef struct _SINGLE_LIST_ENTRY
+{
+    PSINGLE_LIST_ENTRY Next;
+} SINGLE_LIST_ENTRY, *PSINGLE_LIST_ENTRY;
+
+/* Header for a sequenced single linked list union definition */
+typedef union _SINGLE_LIST_HEADER
+{
+    ULONGLONG Alignment;
+    union
+    {
+        struct
+        {
+            SINGLE_LIST_ENTRY Next;
+            USHORT Depth;
+            USHORT Sequence;
+        };
+        ULONGLONG Region;
+    };
+} SINGLE_LIST_HEADER, *PSINGLE_LIST_HEADER;
+
 /* 128-bit 16-byte aligned XMM register */
 typedef struct _M128
 {
diff --git a/sdk/xtdk/xtstruct.h b/sdk/xtdk/xtstruct.h
index 19d2e6f..7bb4924 100644
--- a/sdk/xtdk/xtstruct.h
+++ b/sdk/xtdk/xtstruct.h
@@ -225,6 +225,7 @@ typedef struct _PECOFF_IMAGE_ROM_HEADER PECOFF_IMAGE_ROM_HEADER, *PPECOFF_IMAGE_
 typedef struct _PECOFF_IMAGE_ROM_OPTIONAL_HEADER PECOFF_IMAGE_ROM_OPTIONAL_HEADER, *PPECOFF_IMAGE_ROM_OPTIONAL_HEADER;
 typedef struct _PECOFF_IMAGE_SECTION_HEADER PECOFF_IMAGE_SECTION_HEADER, *PPECOFF_IMAGE_SECTION_HEADER;
 typedef struct _PECOFF_IMAGE_VXD_HEADER PECOFF_IMAGE_VXD_HEADER, *PPECOFF_IMAGE_VXD_HEADER;
+typedef struct _SINGLE_LIST_ENTRY SINGLE_LIST_ENTRY, *PSINGLE_LIST_ENTRY;
 typedef struct _STRING STRING, *PSTRING;
 typedef struct _STRING32 STRING32, *PSTRING32;
 typedef struct _STRING64 STRING64, *PSTRING64;
@@ -242,5 +243,6 @@ typedef union _EFI_IP_ADDRESS EFI_IP_ADDRESS, *PEFI_IP_ADDRESS;
 typedef union _EFI_PXE_BASE_CODE_PACKET EFI_PXE_BASE_CODE_PACKET, *PEFI_PXE_BASE_CODE_PACKET;
 typedef union _LARGE_INTEGER LARGE_INTEGER, *PLARGE_INTEGER;
 typedef union _ULARGE_INTEGER ULARGE_INTEGER, *PULARGE_INTEGER;
+typedef union _SINGLE_LIST_HEADER SINGLE_LIST_HEADER, *PSINGLE_LIST_HEADER;
 
 #endif /* __XTDK_XTSTRUCT_H */