diff --git a/sbin/fsck_ffs/setup.c b/sbin/fsck_ffs/setup.c
index d69beff..3099b5f 100644
--- a/sbin/fsck_ffs/setup.c
+++ b/sbin/fsck_ffs/setup.c
@@ -436,6 +436,7 @@ sblock_init(void)
 	if (sblk.b_un.b_buf == NULL || asblk.b_un.b_buf == NULL)
 		errx(EEXIT, "cannot allocate space for superblock");
 	dev_bsize = secsize = DEV_BSIZE;
+	sblock.fs_bsize = MAXBSIZE;	/* for bufinit() */
 }
 
 /*