update-alternatives error on firefox install

[Pierre Frenkiel]

hi,
Up to now, I was using the iceweasel provided by the Debian repository.
Today, I found in the http://mozilla.debian.net/ site

WARNING: Iceweasel is gone. Please update your apt sources.

So, I added the recommended line into my sources.list

deb http://mozilla.debian.net/ jessie-backports firefox-release

then : apt-get update
apt-get install -t jessie-backports firefox

this gave;
update-alternatives: error: alternative path /usr/bin/firefox doesn't exist

which was true: /usr/bin/firefox was actually missing.
Nevertheless, after doing
ln -s /usr/lib/firefox/firefox /usr/bin/firefox

firefox works, but that doesn't seem the normal way to install it.
Did I miss something, or is this a bug?

best regards,
--
Pierre Frenkiel