-CURRENT (BETA1) zfs pool recognized as corrupted

hi
I've tried to import my zfs pool on:
FreeBSD-9.0-BETA1-amd64-memstick.img
My system currently runs 9.0-BETA1 and pool works correctly.
zpool import returns:

  pool: zroot
    id: 3239789026273107181
 state: FAULTED
status: One or more devices contains corrupted data.
action: The pool cannot be imported due to damaged devices or data.
The pool may be active on another system, but can be imported using
the '-f' flag.
   see: http://www.sun.com/msg/ZFS-8000-5E
config:

zroot                  FAULTED  corrupted data
  9327291201483595311  UNAVAIL  corrupted data

gpart show lists all my partitions
=>       34  250069613  ada0  GPT  (119G)
         34        128     1  freebsd-boot  (64k)
        162       1886     5  bios-boot  (943k)
       2048   16777216     2  !0fc63daf-8483-4772-8e79-3d69d8477de4  (8.0G)
   16779264   33554432     3  freebsd-ufs  (16G)
   50333696  199735951     4  freebsd-zfs  (95G)

My pool 'zroot' consists of partition 4.

I'm able to import this pool on 8.2-RELEASE, booted from CD:
  pool: zroot
    id: 3239789026273107181
 state: ONLINE
action: The pool can be imported using its name or numeric identifier.
config:

zroot                                         ONLINE
  gptid/9795c3f7-b191-11e0-94fb-e89a8f131096  ONLINE

Pool properties:
NAME   PROPERTY       VALUE       SOURCE
zroot  size           95G         -
zroot  used           70.5G       -
zroot  available      24.5G       -
zroot  capacity       74%         -
zroot  altroot        -           default
zroot  health         ONLINE      -
zroot  guid           3239789026273107181  default
zroot  version        15          default
zroot  bootfs         zroot       local
zroot  delegation     on          default
zroot  autoreplace    off         default
zroot  cachefile      -           default
zroot  failmode       panic       local
zroot  listsnapshots  off         default

I'm running zpool at version 15.