APT auth credentials not forwarded

Is there a way to use auth.conf.d credentials with acng?

I have a HTTPS upstream https://something. That entry I replaced with http://HTTPS///something.

This server needs credentials, however. I tried adding a machine HTTPS///something login myusername password mypassword entry but I get a [401] unauthorized response nontetheless.

So, it seems like these credentials are not forwarded.