PVS-Studio warning V501 for OpenCV

CV_IMPL CvMat*
cv2DRotationMatrix( CvPoint2D32f center, double angle,
                    double scale, CvMat* matrix )
{
  cv::Mat M0 = cv::cvarrToMat(matrix),
          M = cv::getRotationMatrix2D(center, angle, scale);
  CV_Assert( M.size() == M.size() );
  M.convertTo(M0, M0.type());
  return matrix;
}

This suspicious code was found in OpenCV project by PVS-Studio static code analyzer.
Warning message is:
V501 There are identical sub-expressions to the left and to the right of the '==' operator: M.size() == M.size() imgwarp.cpp 3672

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/