diff --git a/draft-ietf-quic-transport.md b/draft-ietf-quic-transport.md
index ad565ab17a..34b1b88f28 100644
--- a/draft-ietf-quic-transport.md
+++ b/draft-ietf-quic-transport.md
@@ -1811,7 +1811,7 @@ This document limits migration of connections to new client addresses, except as
 described in {{preferred-address}}. Clients are responsible for initiating all
 migrations.  Servers do not send non-probing packets (see {{probing}}) toward a
 client address until they see a non-probing packet from that address.  If a
-client receives packets from an unknown server address, the client MAY discard
+client receives packets from an unknown server address, the client MUST discard
 these packets.