diff --git a/sdk/include/xdk/winnt_old.h b/sdk/include/xdk/winnt_old.h
index 94d603073a8..569e9e10fc1 100644
--- a/sdk/include/xdk/winnt_old.h
+++ b/sdk/include/xdk/winnt_old.h
@@ -1442,6 +1442,9 @@ typedef struct _RUNTIME_FUNCTION {
     DWORD UnwindData;
 } RUNTIME_FUNCTION,*PRUNTIME_FUNCTION;
 
+#ifndef _APISETRTLSUPPORT_
+#define _APISETRTLSUPPORT_
+
 #define UNWIND_HISTORY_TABLE_SIZE 12
 
 typedef struct _UNWIND_HISTORY_TABLE_ENTRY
@@ -1462,6 +1465,8 @@ typedef struct _UNWIND_HISTORY_TABLE
     UNWIND_HISTORY_TABLE_ENTRY Entry[UNWIND_HISTORY_TABLE_SIZE];
 } UNWIND_HISTORY_TABLE, *PUNWIND_HISTORY_TABLE;
 
+#endif /* _APISETRTLSUPPORT_ */
+
 typedef
 _Function_class_(GET_RUNTIME_FUNCTION_CALLBACK)
 PRUNTIME_FUNCTION