diff --git a/ndn-cpp/transport/TcpTransport.cpp b/ndn-cpp/transport/TcpTransport.cpp
index 1f575b9..69a9869 100644
--- a/ndn-cpp/transport/TcpTransport.cpp
+++ b/ndn-cpp/transport/TcpTransport.cpp
@@ -28,7 +28,7 @@
   ndn_ = &ndn;
 }
 
-void TcpTransport::send(unsigned char *data, unsigned int dataLength)
+void TcpTransport::send(const unsigned char *data, unsigned int dataLength)
 {
   ndn_Error error;
   if (error = ndn_TcpTransport_send(&transport_, data, dataLength))