need to downgrade libc6!

[Jaume Teixi <teixi@6tems.com>]

I've upgraded libc6 to 2.1.95 but need to downgrade to 2.1.3 due to
connection to a database

I've stable on sources.list but apt tells:

# apt-get -f install --reinstall libc6
Reading Package Lists... Done
Building Dependency Tree... Done
Sorry, re-installation of libc6 is not possible, it cannot be downloaded

how to fix this ?

thanks,
jaume.