diff --git a/src/data.hpp b/src/data.hpp
index 078938a..b12061b 100644
--- a/src/data.hpp
+++ b/src/data.hpp
@@ -310,7 +310,7 @@
   bool
   operator!=(const Data& other) const;
 
-private:
+protected:
   /**
    * @brief Clear the wire encoding.
    */