Create closes/periodic edge from points

Hi,

I habe a lot of points which describe a contour. Now I need to get a wire from the point list.

//
GeomAPI_PointsToBSpline toBSpline(const PointVec& points)
{
TColgp_Array1OfPnt arr(0,points.size()-1);
for(unsigned int i = 0;i {
arr.SetValue(i,gp_Pnt(points[i].X(),points[i].Y(),points[i].Z()));
}

auto spline = GeomAPI_PointsToBSpline(arr);
spline.Curve()->SetPeriodic();

return spline;
}

OpenCascades creates the curve (testet it with the step export). My problem is the connection between last and first point. There I have a big failure. You can see it in the attached picture. Seems that I do something wrong the make the spline periodic.
I also tested GeomAPI_Interpolate, but there a runtime error occurs.
So, what did I wrong?

Best regards

Pellaeon