PVS-Studio warning V547 for Apache

typedef UINT_PTR SOCKET;

static unsigned int __stdcall win9x_accept(void * dummy)
{
  SOCKET csd;
  ...
  do {
      clen = sizeof(sa_client);
      csd = accept(nsd, (struct sockaddr *) &sa_client, &clen);
  } while (csd < 0 &&
           APR_STATUS_IS_EINTR(apr_get_netos_error()));
  ...
}

This suspicious code was found in Apache project by PVS-Studio static code analyzer.
Warning message is:
V547 Expression 'csd < 0' is always false. Unsigned type value is never < 0. libhttpd child.c 404

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/