Calling WCF Service with ProtoBehavior and Multiple Parameters

This puzzles me, and I was hoping it was a stupid mistake on my part. When I call the next web service, if a null parameter is encountered, then all of the following parameters are zero (or zero for numbers).

[OperationContract, ProtoBehavior]
[ServiceKnownType(typeof(ServiceFault))]
[FaultContract(typeof(ServiceFault))]
PersonProfileMessagePart Create(ObjectId person, ObjectId industry, int yearsInIndustry, ObjectId occupation, string occupationFreeText,
                                int yearsInOccupation, string maritalStatus, string educationLevel, 
                                List<ChildMessagePart> children, FinancialProfileMessagePart financialProfile,
                                List<ObjectId> traits);

      

        
        
        
      

    

For example, if person

and yearsInIndustry

, but not industry

, all parameters, including yearsInIndustry

the default, are zero / zero. Is there an additional attribute I need to apply?

{edit} Sorry. Mark, this is WCF with a custom binding.

<customBinding>
    <binding name="ServiceFedBinding">
        <security authenticationMode="SecureConversation">
            <secureConversationBootstrap authenticationMode="IssuedToken">
                <issuedTokenParameters tokenType="http://docs.oasis-open.org/wss/oasis-wss-saml-token-profile-1.1#SAMLV1.1">
                    <issuer address="http://links-dev:91/security/authentication/securetokenservice.svc/" binding="wsHttpBinding">
                        <identity>
                            <dns value="LINKS"/>
                        </identity>
                    </issuer>
                    <issuerMetadata address="http://links-dev:91/security/authentication/securetokenservice.svc/mex"/>
                </issuedTokenParameters>
            </secureConversationBootstrap>
        </security>

      

        
        
        
      

    

Thanks in advance. Mike