PVS-Studio warning V547 for Chromium

typedef UINT_PTR SOCKET;

SOCKET socket_;

int TCPServerSocketWin::Listen(....) {
  ....
  socket_ = socket(address.GetSockAddrFamily(),
                   SOCK_STREAM, IPPROTO_TCP);
  if (socket_ < 0) {
    PLOG(ERROR) << "socket() returned an error";
    return MapSystemError(WSAGetLastError());
  }
  ....
}

This suspicious code was found in Chromium project by PVS-Studio static code analyzer.
Warning message is:
V547 Expression 'socket_ < 0' is always false. Unsigned type value is never < 0. tcp_server_socket_win.cc 48

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/