ZFS: unknown file system on boot

I use zfs on root setup with system r258777. I've tried my kernel and
generic one.

I found new  feature from r257650 that now loader.4th will load modules
after menu gone (kernel selection). Now I have problem that modules won't
loaded even I selected default kernel.

for example, I have following contents of /boot/loader.conf, but none of
modules will be loaded:
zfs_load="YES"
if_re_load="YES"

Later on boot I got that system can't  find filesystem zfs! If I break
loader menu and manually load modules one by one, anything will be OK.

How to boot my system correctly?

-- Eir Nym