diff --git a/rtl/win16/wintypes.inc b/rtl/win16/wintypes.inc
index c2173c176d..f7fbbeffd0 100644
--- a/rtl/win16/wintypes.inc
+++ b/rtl/win16/wintypes.inc
@@ -1905,3 +1905,7 @@ type
     dwExtraInfo: DWORD;
   end;
   TMouseHookStruct = MOUSEHOOKSTRUCT;
+
+const
+{ Mode control }
+  WM_CANCELMODE = $001F;