diff --git a/ndn-cpp/transport/transport.hpp b/ndn-cpp/transport/transport.hpp
index ed3e240..512a003 100644
--- a/ndn-cpp/transport/transport.hpp
+++ b/ndn-cpp/transport/transport.hpp
@@ -37,7 +37,7 @@
    * @param dataLength The number of bytes in data.
    */
   virtual void 
-  send(const uint8_t *data, unsigned int dataLength);
+  send(const uint8_t *data, size_t dataLength);
   
   void 
   send(const std::vector<uint8_t>& data)