diff --git a/ndn-cpp/encoding/BinaryXMLWireFormat.hpp b/ndn-cpp/encoding/BinaryXMLWireFormat.hpp
index 5b3d065..ad3a88c 100644
--- a/ndn-cpp/encoding/BinaryXMLWireFormat.hpp
+++ b/ndn-cpp/encoding/BinaryXMLWireFormat.hpp
@@ -12,10 +12,10 @@
 
 class BinaryXMLWireFormat : public WireFormat {
 public:
-  virtual void encodeName(Name &name, std::vector<unsigned char> &output);
+  virtual void encodeName(const Name &name, std::vector<unsigned char> &output);
   virtual void decodeName(Name &name, const unsigned char *input, unsigned int inputLength);
 
-  virtual void encodeInterest(Interest &interest, std::vector<unsigned char> &output);
+  virtual void encodeInterest(const Interest &interest, std::vector<unsigned char> &output);
   virtual void decodeInterest(Interest &interest, const unsigned char *input, unsigned int inputLength);
   
   static BinaryXMLWireFormat &instance() { return instance_; }