diff --git a/include/wx/defs.h b/include/wx/defs.h
index e4b38e1001..a27d2371c3 100644
--- a/include/wx/defs.h
+++ b/include/wx/defs.h
@@ -126,7 +126,7 @@
 // Digital Unix C++ compiler only defines this symbol for .cxx and .hxx files,
 // so define it ourselves
 #ifdef __DECCXX
-#ifndef VMS
+#ifndef __VMS
 # define __cplusplus
 #endif
 #endif // __DECCXX