diff --git a/include/wx/defs.h b/include/wx/defs.h
index 6271188f53..e9fa47859e 100644
--- a/include/wx/defs.h
+++ b/include/wx/defs.h
@@ -896,6 +896,7 @@ typedef void *          WXRGNDATA;
 typedef void *          WXMSG;
 typedef unsigned long   WXHCONV;
 typedef unsigned long   WXHKEY;
+typedef unsigned long   WXHTREEITEM;
 typedef void *          WXDRAWITEMSTRUCT;
 typedef void *          WXMEASUREITEMSTRUCT;
 typedef void *          WXLPCREATESTRUCT;