diff --git a/net/ipv6/ah6.c b/net/ipv6/ah6.c
index a8221d1..67cd066 100644
--- a/net/ipv6/ah6.c
+++ b/net/ipv6/ah6.c
@@ -477,8 +477,15 @@
 
 	x->props.header_len = XFRM_ALIGN8(sizeof(struct ip_auth_hdr) +
 					  ahp->icv_trunc_len);
-	if (x->props.mode == XFRM_MODE_TUNNEL)
+	switch (x->props.mode) {
+	case XFRM_MODE_BEET:
+	case XFRM_MODE_TRANSPORT:
+		break;
+	case XFRM_MODE_TUNNEL:
 		x->props.header_len += sizeof(struct ipv6hdr);
+	default:
+		goto error;
+	}
 	x->data = ahp;
 
 	return 0;