diff --git a/drivers/scsi/scsi.c b/drivers/scsi/scsi.c
index 32979fe..73994e2 100644
--- a/drivers/scsi/scsi.c
+++ b/drivers/scsi/scsi.c
@@ -565,7 +565,8 @@
 	/* 
 	 * If SCSI-2 or lower, store the LUN value in cmnd.
 	 */
-	if (cmd->device->scsi_level <= SCSI_2) {
+	if (cmd->device->scsi_level <= SCSI_2 &&
+	    cmd->device->scsi_level != SCSI_UNKNOWN) {
 		cmd->cmnd[1] = (cmd->cmnd[1] & 0x1f) |
 			       (cmd->device->lun << 5 & 0xe0);
 	}