PVS-Studio warning V576 for FlightGear

unsigned int getPort() const ;

void
UGTelnet::handleAccept()
{
  ....
  printf("Telent server accepted connection from %s:%d\n",
         addr.getHost(), addr.getPort() );
  ....
}

This suspicious code was found in FlightGear project by PVS-Studio static code analyzer.
Warning message is:
V576 Incorrect format. Consider checking the third actual argument of the 'printf' function. The SIGNED integer type argument is expected. ugear_telnet.cxx 230

PVS-Studio is a static analyzer for detecting bugs in the source code of applications written in C, C++, C++11, C++/CX. Site: http://www.viva64.com/en/pvs-studio/