ssh agent-forwarding with lxc

I have a "little" problem

I try to ssh using putty and pageant to server, than to ssh into lxc-container and than to other server. But no publickey is used, it prompts for password (at last hop).

But When I shorten path and ssh from host not from container - everything works...

All sshd configs are pure debian installation - now I tried to add AllowAgentForwarding yes - but nothing changed.

My Putty has Both AllowForwarding and Allow User changes set.

The only thing I see which differs - is $SSH_AUTH_SOCK - it is not set on container... But how to set it?