diff --git a/include/wx/radiobox.h b/include/wx/radiobox.h
index d5d0582026..6807523119 100644
--- a/include/wx/radiobox.h
+++ b/include/wx/radiobox.h
@@ -12,6 +12,8 @@
 #ifndef _WX_RADIOBOX_H_BASE_
 #define _WX_RADIOBOX_H_BASE_
 
+#include "wx/defs.h"
+
 #if wxUSE_RADIOBOX
 
 #include "wx/ctrlsub.h"