OFFSET function converts ARC into SPLINE, how to prevent that?

Hi,

I made some simple drawings containing arcs. Now I wanted to offset these arcs so they would be smaller (compensation for my CNC tool radius for making inner cuts). The offset function works great but it turns my arcs into splines... My DXF conversion tools don't handle splines and also have issues with polylines when I save it to R12 format. (it works but I get strange output resulting in unpractical toolpaths)

The workaround for me today is to manually remove the splines after offsetting and redraw them again with the arc tool. Because I only have a few arcs in my design today this is not a big issue but it would be great if there is a way to control the output of the offset function (ie. allow / disallow spline creation )

Thanks!