Hi, First, today when running guix import opam iter, I get a synopsis, and #f as the description because the field is missing.
I also pushed a small patch to master, as 24aa7b3c21309b63cc6e8e18d6417d2cddccf6c6, that ensures that, when the field exists but contains unknown data, we also return #f instead of a match error that produces the ugly backtrace you saw. Thanks for the report, closing :)
