diff --git a/reactos/include/psdk/winuser.h b/reactos/include/psdk/winuser.h
index 6008e757c99..dd1ba77bcdf 100644
--- a/reactos/include/psdk/winuser.h
+++ b/reactos/include/psdk/winuser.h
@@ -269,6 +269,7 @@ extern "C" {
 #define BS_MULTILINE	0x2000
 #define BS_NOTIFY	0x4000
 #define BS_OWNERDRAW	0xb
+#define BS_TYPEMASK	0xFL
 #define BS_PUSHBUTTON	0
 #define BS_PUSHLIKE	4096
 #define BS_RADIOBUTTON 4