diff --git a/samples/mdi/mdi.cpp b/samples/mdi/mdi.cpp
index 423a2447be..19d784f35c 100644
--- a/samples/mdi/mdi.cpp
+++ b/samples/mdi/mdi.cpp
@@ -17,6 +17,11 @@
 // headers
 // ---------------------------------------------------------------------------
 
+#ifdef __VMS
+#define XtDisplay XTDISPLAY
+#define XtWindow XTWINDOW
+#endif
+
 // For compilers that support precompilation, includes "wx/wx.h".
 #include "wx/wxprec.h"