When exporting markdown with ToC, if heading numbering is not enabled, it
would fail with the attached backtrace. The cause is that the function
`org-md--build-toc' in `ox-md.el' does not properly handle this case which
effectively results in a function call `(format "%d." nil)'. In my patch,
when
Remember to cover the basics, that is, what you expected to happen and
what in fact did happen. You don't know how to make a good report? See
http://orgmode.org/manual/Feedback.html#Feedback
Your bug report will be posted to the Org-mode mailing list.
-