diff --git a/reactos/w32api/include/ddk/winddk.h b/reactos/w32api/include/ddk/winddk.h
index d86452a594a..2d3ac42636b 100644
--- a/reactos/w32api/include/ddk/winddk.h
+++ b/reactos/w32api/include/ddk/winddk.h
@@ -4118,7 +4118,8 @@ typedef struct _KWAIT_BLOCK {
   PVOID  Object;
   struct _KWAIT_BLOCK * RESTRICTED_POINTER  NextWaitBlock;
   USHORT  WaitKey;
-  USHORT  WaitType;
+  UCHAR WaitType;
+  UCHAR SpareByte;
 } KWAIT_BLOCK, *PKWAIT_BLOCK, *RESTRICTED_POINTER PRKWAIT_BLOCK;
 
 typedef struct _IO_REMOVE_LOCK_TRACKING_BLOCK * PIO_REMOVE_LOCK_TRACKING_BLOCK;