diff --git a/common/fltk/FL/Fl_Widget.H b/common/fltk/FL/Fl_Widget.H
index 5cc6a79..041b2d3 100644
--- a/common/fltk/FL/Fl_Widget.H
+++ b/common/fltk/FL/Fl_Widget.H
@@ -108,6 +108,7 @@
  */
 class FL_EXPORT Fl_Widget {
   friend class Fl_Group;
+  friend class Fl_X;
 
   Fl_Group* parent_;
   Fl_Callback* callback_;