diff --git a/include/wx/listbook.h b/include/wx/listbook.h
index c6a78fc706..f77b0ca690 100644
--- a/include/wx/listbook.h
+++ b/include/wx/listbook.h
@@ -112,6 +112,10 @@ private:
     // common part of all constructors
     void Init();
 
+    // this should be called when we need to be relaid out
+    void UpdateSize();
+
+
     DECLARE_EVENT_TABLE()
     DECLARE_DYNAMIC_CLASS_NO_COPY(wxListbook)
 };