zfs root is not mounted automatically

Hello,
I have successfullty moved my root to zfs (some work, though) following 
Pawel instruction.
Anyway, it still refuses to boot without asking root device from cmd line :

acd0: DVDR <DVDRW IDE 16X/VER A091> at ata0-master UDMA66
ad10: 238475MB <Seagate ST3250624AS 3.AAE> at ata5-master SATA150
ad12: 305245MB <External Disk 0 RGL10364> at ata6-master SATA150
pcm0: <HDA Codec: Realtek ALC882>
pcm0: <HDA Driver Revision: 20070505_0044>
WARNING: ZFS is considered to be an experimental feature in FreeBSD.
SMP: AP CPU #1 Launched!
Trying to mount root from zfs:system

Manual root filesystem specification:
  <fstype>:<device>  Mount <device> using filesystem <fstype>
                       eg. ufs:da0s1a
  ?                  List valid disk boot devices
  <empty line>       Abort manual input

mountroot> ZFS filesystem version 6
ZFS storage pool version 6
zfs:system
Trying to mount root from zfs:system
fuse4bsd: version 0.3.0, FUSE ABI 7.8

It first fails to mount my zfs:system
I get the mountroot cmd line, and if I type zfs:system, boot resumes and 
completes allright.

Any idea of how to get rid of this ?

vil1 ~ # uname -a
FreeBSD vil1.ruomad.net 7.0-CURRENT FreeBSD 7.0-CURRENT #2: Sat May 12 
08:10:27 CEST 2007     root_at_vil1.ruomad.net:/usr/obj/usr/src/sys/VIL1  amd64

vil1 ~ # zpool list
NAME                    SIZE    USED   AVAIL    CAP  HEALTH     ALTROOT
data                    298G   64.3G    234G    21%  ONLINE     -
system                 74.5G   10.3G   64.2G    13%  ONLINE     -

vil1 ~ # df
Filesystem       1K-blocks     Used     Avail Capacity  Mounted on
system            66604544   497024  66107520     1%    /
devfs                    1        1         0   100%    /dev
/dev/ad10s2a        507630   418978     48042    90%    /bootdisk
system/tmp        66110464     2944  66107520     0%    /tmp
system/usr        70144768  4037248  66107520     6%    /usr
system/usr/local  68888704  2781184  66107520     4%    /usr/local
system/var        67045760   938240  66107520     1%    /var
/dev/ad10s1      122093968 35128468  86965500    29%    /mnt/win
data             307590016 67431168 240158848    22%    /data

Thanks in advance

Bruno