fsck_ufs: cannot alloc 3166749884 bytes for inoinfo

A recent panic left my FS with some serious corruption, which fsck is
unable to repair:

# fsck_ufs -b 376512 -fy /var
Alternate super block location: 376512
** /dev/twed0s1e
** Last Mounted on
** Phase 1 - Check Blocks and Sizes
fsck_ufs: cannot alloc 3166749884 bytes for inoinfo

(same holds for any superblock I've tried).

How can I recover from this, short of running newfs?

Kris