diff --git a/draft-ietf-quic-tls.md b/draft-ietf-quic-tls.md
index 6db7ed7002..620146202d 100644
--- a/draft-ietf-quic-tls.md
+++ b/draft-ietf-quic-tls.md
@@ -1424,10 +1424,11 @@ without needing to receive the first packet that triggered the change.  An
 endpoint that notices a changed Key Phase bit updates keys and decrypts the
 packet that contains the changed value.
 
-This mechanism replaces the TLS KeyUpdate message.  Endpoints MUST NOT send a
+This mechanism replaces the key update mechanism of TLS, which relies on
+KeyUpdate messages sent using 1-RTT encryption keys.  Endpoints MUST NOT send a
 TLS KeyUpdate message.  Endpoints MUST treat the receipt of a TLS KeyUpdate
-message as a connection error of type 0x10a, equivalent to a fatal TLS alert of
-unexpected_message (see {{tls-errors}}).
+message in a 1-RTT packet as a connection error of type 0x10a, equivalent to a
+fatal TLS alert of unexpected_message; see {{tls-errors}}.
 
 {{ex-key-update}} shows a key update process, where the initial set of keys used
 (identified with @M) are replaced by updated keys (identified with @N).  The