diff --git a/drivers/firewire/fw-sbp2.c b/drivers/firewire/fw-sbp2.c
index ea4811c..60ebcb5 100644
--- a/drivers/firewire/fw-sbp2.c
+++ b/drivers/firewire/fw-sbp2.c
@@ -1473,6 +1473,10 @@
 {
 	struct sbp2_logical_unit *lu = sdev->hostdata;
 
+	/* (Re-)Adding logical units via the SCSI stack is not supported. */
+	if (!lu)
+		return -ENOSYS;
+
 	sdev->allow_restart = 1;
 
 	/*