typo/bug in function cvProjectPoints2 ?

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A typo/bug in modules\calib3d\calibration.cpp, function cvProjectPoints2 ?

According to the distortion definition we have:

xd = x*cdist*icdist2 + k[2]*a1 + k[3]*a2;  (line 1007)

 yd = y*cdist*icdist2 + k[2]*a3 + k[3]*a1;

 m[i].x = xd*fx + cx;

 m[i].y = yd*fy + cy;

where 
a1 = 2*x*y;
 a2 = r2 + 2*x*x;
 a3 = r2 + 2*y*y;

whereas a derivative (line 1080)

double dmxdt = fx*(dxdt[j]*cdist*icdist2 + x*dcdist_dt*icdist2 + x*cdist*dicdist2_dt +
                                       k[2]*da1dt + k[3]*(dr2dt + 2*x*dxdt[j]));

Should the last term be equal 4*x*dxdt[j] ?

Similar places in calculations of dmydt, dmxdr, and dmydr