npostavs@users.sourceforge.net writes:

> The following appears to fix it, though perhaps we should use a smarter
> equal function that would consider the circular lists to actually be
> equal instead of bailing out and returning nil on circularity.

Thanks for tracking this one down and making a patch, which looks good
to me. Does that smarter equal function already exist? It doesn't seem
worth the effort of writing one for this purpose only.

Here is a test to add to your patch, which fails without it and passes
with it: