diff --git a/sdk/include/reactos/x86x64/Cpuid.h b/sdk/include/reactos/x86x64/Cpuid.h
index 3c317ccea62..4e80cbd44c7 100644
--- a/sdk/include/reactos/x86x64/Cpuid.h
+++ b/sdk/include/reactos/x86x64/Cpuid.h
@@ -114,6 +114,20 @@ typedef union
     };
 } CPUID_EXTENDED_STATE_SUB_LEAF_REGS;
 
+// CPUID_EXTENDED_STATE (0x0D)
+// CPUID_EXTENDED_STATE_SIZE_OFFSET (0x02 .. 0x1F)
+typedef union
+{
+    INT32 AsInt32[4];
+    struct
+    {
+        UINT32 Size;
+        UINT32 Offset;
+        CPUID_EXTENDED_STATE_SIZE_OFFSET_ECX Ecx;
+        UINT32 Edx;
+    };
+} CPUID_EXTENDED_STATE_SIZE_OFFSET_REGS;
+
 // CPUID_EXTENDED_CPU_SIG (0x80000001)
 typedef union
 {