diff --git a/hw/scsi/scsi-disk.c b/hw/scsi/scsi-disk.c
index e0d79c7966..477ee2bcd4 100644
--- a/hw/scsi/scsi-disk.c
+++ b/hw/scsi/scsi-disk.c
@@ -1628,9 +1628,10 @@ static void scsi_disk_emulate_mode_select(SCSIDiskReq *r, uint8_t *inbuf)
          * Since the existing code only checks/updates bits 8-15 of the block
          * size, restrict ourselves to the same requirement for now to ensure
          * that a block size set by a block descriptor and then read back by
-         * a subsequent SCSI command will be the same
+         * a subsequent SCSI command will be the same. Also disallow a block
+         * size of 256 since we cannot handle anything below BDRV_SECTOR_SIZE.
          */
-        if (bs && !(bs & ~0xff00) && bs != s->qdev.blocksize) {
+        if (bs && !(bs & ~0xfe00) && bs != s->qdev.blocksize) {
             s->qdev.blocksize = bs;
             trace_scsi_disk_mode_select_set_blocksize(s->qdev.blocksize);
         }