diff --git a/FL/Fl_Device.H b/FL/Fl_Device.H
index 4118d81..c8f1393 100644
--- a/FL/Fl_Device.H
+++ b/FL/Fl_Device.H
@@ -511,6 +511,8 @@ class Fl_Cairo_Graphics_Driver : public Fl_Xlib_Graphics_Driver {
     
 public:
 
+    static const char *class_id;
+
 //    void set_current(void);
 
     Fl_Cairo_Graphics_Driver ( );