diff --git a/rfb/Configuration.h b/rfb/Configuration.h
index 20aec99..d50c1cb 100644
--- a/rfb/Configuration.h
+++ b/rfb/Configuration.h
@@ -97,6 +97,7 @@
     virtual char* getDefaultStr() const;
     virtual char* getValueStr() const;
     virtual bool isBool() const;
+    virtual void setImmutable();
   private:
     VoidParameter* param;
   };