apt: conf file says: /tmp/cache/apt/. Apt insists on /var/cache/apt/archives/

[shaulk@israsrv.net.il (shaul)]

How can I fixed it ?

Package: apt
Version: 0.3.11.1

[09:21:40 shaul]# apt-get install xbooks
Reading Package Lists... Done
Building Dependency Tree... Done
1 packages upgraded, 0 newly installed, 0 to remove and 120 not upgraded.
E: Sorry, you don't have enough free space in /var/cache/apt/archives/
[09:27:04 shaul]# grep 'Cache "/' /etc/apt/apt.conf
  Cache "/tmp/cache/apt/" {
[09:27:10 shaul]#ls -Rl /tmp/cache/
/tmp/cache:
total 1
drwxr-xr-x   3 root     root         1024 Sep 29 09:29 apt

/tmp/cache/apt:
total 1
drwxr-xr-x   3 root     root         1024 Sep 29 09:29 archives

/tmp/cache/apt/archives:
total 1
drwxr-xr-x   2 root     root         1024 Sep 29 09:29 partial

/tmp/cache/apt/archives/partial:
total 0
[09:30:37 shaul]#

-- System Information
Debian Release: potato
Kernel Version: Linux rakefet 2.0.36 #2 Sun Feb 21 15:55:27 EST 1999 i586 
unknown

Versions of the packages apt depends on:
ii  libc6           2.1.2-5        GNU C Library: Shared libraries and timezone
ii  libstdc++2.9    2.91.66-0slink The GNU stdc++ library (egcs version)