diff --git a/include/wx/msgdlg.h b/include/wx/msgdlg.h
index 8e0e0a9bb7..3e52b9c68d 100644
--- a/include/wx/msgdlg.h
+++ b/include/wx/msgdlg.h
@@ -158,7 +158,7 @@ public:
         wxASSERT_MSG( !(style & wxCANCEL_DEFAULT) || (style & wxCANCEL),
                       "wxCANCEL_DEFAULT is invalid without wxCANCEL" );
 
-        wxASSERT_MSG( !(style & wxCANCEL_DEFAULT) || !(style & wxNO),
+        wxASSERT_MSG( !(style & wxCANCEL_DEFAULT) || !(style & wxNO_DEFAULT),
                       "only one default button can be specified" );
 
         m_dialogStyle = style;