should -> must

draft-ietf-quic-transport.md

@@ -634,10 +634,9 @@ packet in response, then it sets the Destination Connection ID to the value from
 the Source Connection ID in the Retry packet. Changing Destination Connection ID
 also results in a change to the keys used to protect the Initial packet. It also
 sets the Token field to the token provided in the Retry. Additionally, the
-client SHOULD NOT change the Source Connection ID because the server may include
+client MUST NOT change the Source Connection ID because the server may include
 the connection ID as part of its token validation logic. If the client changes
-the Source Connection ID in this case, it would likely trigger a new Retry to be
-sent.
+the Source Connection ID in this case it could trigger a new Retry to be sent.
 
 When a server receives an Initial packet with an address validation token, it
 SHOULD attempt to validate it.  If the token is invalid then the server SHOULD