diff --git a/demo/digesttreescene.h b/demo/digesttreescene.h
index 0d98f7e..1915c2f 100644
--- a/demo/digesttreescene.h
+++ b/demo/digesttreescene.h
@@ -11,6 +11,7 @@
 
 public:
   DigestTreeScene(QWidget *parent = 0);
+  void plot();
 private:
   ogdf::Graph m_graph;
 };