diff --git a/src/encoding/block.hpp b/src/encoding/block.hpp
index c91d12c..17192d8 100644
--- a/src/encoding/block.hpp
+++ b/src/encoding/block.hpp
@@ -29,6 +29,12 @@
 #include "buffer.hpp"
 #include "tlv.hpp"
 
+namespace boost {
+namespace asio {
+class const_buffer;
+} // namespace asio
+} // namespace boost
+
 namespace ndn {
 
 template<bool> class EncodingImpl;
@@ -281,6 +287,9 @@
   bool
   operator!=(const Block& other) const;
 
+public: // ConvertibleToConstBuffer
+  operator boost::asio::const_buffer() const;
+
 protected:
   ConstBufferPtr m_buffer;