diff --git a/vncviewer/DesktopWindow.h b/vncviewer/DesktopWindow.h
index 3fe9c86..2a4613c 100644
--- a/vncviewer/DesktopWindow.h
+++ b/vncviewer/DesktopWindow.h
@@ -78,6 +78,8 @@
 
   int handle(int event);
 
+  void fullscreen_on();
+
 private:
   static int fltkHandle(int event, Fl_Window *win);