SYSML21 — SendNode production in EBNF is incorrect

SendNode : SendActionUsage =
    OccurrenceUsagePrefix ActionUsageDeclaration? 'send'
    ( ownedRelationship += NodeParameterMember SenderReceiverPart?
      | ownedRelationship += EmptyParameterMember SendReceiverPart )?
    ActionBody

action a2 {
    in s : S;
    action aa {
        out part target;
    }
    flow aa.target to snd.receiver;
    action snd send { 
        in :>> payload = s;
    }
}