diff --git a/ndn-cpp/transport/TcpTransport.cpp b/ndn-cpp/transport/TcpTransport.cpp
index 69a9869..044901b 100644
--- a/ndn-cpp/transport/TcpTransport.cpp
+++ b/ndn-cpp/transport/TcpTransport.cpp
@@ -31,7 +31,7 @@
 void TcpTransport::send(const unsigned char *data, unsigned int dataLength)
 {
   ndn_Error error;
-  if (error = ndn_TcpTransport_send(&transport_, data, dataLength))
+  if (error = ndn_TcpTransport_send(&transport_, (unsigned char *)data, dataLength))
     throw std::runtime_error(ndn_getErrorString(error));  
 }
 
diff --git a/ndn-cpp/transport/Transport.cpp b/ndn-cpp/transport/Transport.cpp
index 4d6024c..0fa97bc 100644
--- a/ndn-cpp/transport/Transport.cpp
+++ b/ndn-cpp/transport/Transport.cpp
@@ -15,7 +15,7 @@
   throw logic_error("unimplemented");
 }
   
-void Transport::send(unsigned char *data, unsigned int dataLength)
+void Transport::send(const unsigned char *data, unsigned int dataLength)
 {
   throw logic_error("unimplemented");
 }