dump | restore fails: unknown tape header type 1853384566

[Mikhail T.]

Hello!

I'm trying to migrate a filesystem from one disk to another using:

    dump a0hCf 0 32 - /old | restore -rf -

(/old is already mounted read-only). The process runs for a while and 
then stops with:

    [...]
      DUMP: 22.85% done, finished in 3:57 at Tue Mar 24 01:03:21 2009
      DUMP: 24.66% done, finished in 3:50 at Tue Mar 24 01:00:58 2009
      DUMP: 26.44% done, finished in 3:43 at Tue Mar 24 00:59:14 2009
    unknown tape header type 1853384566
    abort? [yn]

Any idea, what's going on? Why can't FreeBSD's restore read FreeBSD's 
dump's output?

The system runs 7.0-STABLE from July 6th, i386. I just tried updating 
the dump and restore from source (latest 7.x) -- the error is the same...

Please, advise. Thanks!

    -mi