PVS-Studio warning V547 for WebRTC

typedef UINT_PTR SOCKET;
typedef SOCKET cpr_socket_t;

cpr_socket_t
sip_tcp_create_connection (sipSPIMessage_t *spi_msg)
{
  cpr_socket_t new_fd;
  ....
  new_fd = cprSocket(af_listen, SOCK_STREAM, 0);
  if (new_fd < 0) {
    CCSIP_DEBUG_ERROR(SIP_F_PREFIX"Socket creation failed %d.",
                      fname, cpr_errno);
    return INVALID_SOCKET;
  }
  ....
}

This suspicious code was found in WebRTC project by PVS-Studio static code analyzer.
Warning message is:
V547 Expression 'new_fd < 0' is always false. Unsigned type value is never < 0. ccsip_platform_tcp.c 438

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/