I was playing with dimensions and encountered a problem dimensioning the radius of the edge of a solid.

Steps I took:
1) Draw solid box
2) Draw solid sphere overlapping box
3) Boolean Diff, with sphere as cutting object
4) DimRadius one of the arc edges that the sphere cut

DimRadius command runs but doesn't display an arrow or center point. Clicking on Arrow location and Text location doesn't produce a radius dimension.

Thinking it was due to this being an edge, I selected the edge and copy/paste to create a curve and then tried DimRadius the curve, same results. Am I doing something wrong, or have I stumbled upon a bug? Model attached.

--Larry