Handling conflicting profiles?

[Marc Coquand]

Heya!

I recently upgraded Guix with `guix upgrade`, and now when I try to
reconfigure I get the error

guix system: error: profile contains conflicting entries for nss-certs
guix system: error:   first entry: nss-certs@3.98 
/gnu/store/yyc6chh9l08h030ad6633rn034mqfavr-nss-certs-3.98
guix system: error:   second entry: nss-certs@3.88.1 
/gnu/store/5y39gqnvlfrw9gxyxbqqkdr8cxgp1fa1-nss-certs-3.88.1
hint: You cannot have two different versions or variants of `nss-certs'
in the same profile.

So it seems I need to upgrade the profile somehow, but I do not really
understand how to do so.

Any clue how to fix this type of error?

Thanks in advance,
Marc