diff --git a/reactos/include/messages.h b/reactos/include/messages.h
index 77eb4196d6e..c799adda1bb 100644
--- a/reactos/include/messages.h
+++ b/reactos/include/messages.h
@@ -1050,6 +1050,9 @@ extern "C" {
 #define WM_NCRBUTTONDBLCLK	(166)
 #define WM_NCRBUTTONDOWN	(164)
 #define WM_NCRBUTTONUP	(165)
+#define WM_NCXBUTTONDOWN	(171)
+#define WM_NCXBUTTONUP	(172)
+#define WM_NCXBUTTONDBLCLK	(173)
 #define WM_NEXTDLGCTL	(40)
 #define WM_NOTIFY	(78)
 #define WM_NOTIFYFORMAT	(85)