Squid3 with IPv6 on Debian

[fayax]

I'm trying to enable IPv6 with Squid3 on Debian Lenny.
I added the following directives to squid.conf

acl to_ipv6 dst ipv6
tcp_outgoing_address 2001:xxx:x:xxx::x to_ipv6
tcp_outgoing_address 66.xxx.xxx.xxx !to_ipv6

When I rung "squid3 -k parse", I get this error:

Processing Configuration File: /etc/squid3/squid.conf (depth 0)
FATAL: Bungled squid.conf line 1059: tcp_outgoing_address 2001:xxx:x:xxx::x to_ipv6
Squid Cache (Version 3.0.STABLE8): Terminated abnormally.

Anyone have any idea why I'm getting this error? Any help would greatly be appreciated.