PVS-Studio warning V547 for CamStudio

bool CSoundFile::OpenWaveFile()
{
  ....
  DWORD bytesRead = mmioRead(m_hFile, (LPSTR)&m_Format,
                             m_MMCKInfoChild.cksize);
  if (bytesRead < 0)
  {
    AfxMessageBox("Error reading PCM wave format record");
    mmioClose(m_hFile,0);
    m_Mode = FILE_ERROR;
    return FALSE;
  }
  ....
}

This suspicious code was found in CamStudio project by PVS-Studio static code analyzer.
Warning message is:
V547 Expression 'bytesRead < 0' is always false. Unsigned type value is never < 0. soundfile.cpp 166

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/