diff --git a/net/can/isotp.c b/net/can/isotp.c
index 3ef7f78..e32d446 100644
--- a/net/can/isotp.c
+++ b/net/can/isotp.c
@@ -1228,7 +1228,8 @@ static int isotp_setsockopt(struct socket *sock, int level, int optname,
 			if (ll.mtu != CAN_MTU && ll.mtu != CANFD_MTU)
 				return -EINVAL;
 
-			if (ll.mtu == CAN_MTU && ll.tx_dl > CAN_MAX_DLEN)
+			if (ll.mtu == CAN_MTU &&
+			    (ll.tx_dl > CAN_MAX_DLEN || ll.tx_flags != 0))
 				return -EINVAL;
 
 			memcpy(&so->ll, &ll, sizeof(ll));