Modifying REST.DocServer to use new %Object instead of %ZEN.proxyObject

I was trying to modify the REST.DocServer sample in the SAMPLE namespaces to use the new %Object and %Array system objects (Ensemble 2016.2 build 636) with the following changes:

/// This method returns a list of namespaces for this server

ClassMethod GetNamespaces() As %Status

{

    #dim tSC As %Status = $$$OK

    #dim tList,tNS,tFilteredList,tValue As %String

    #; Get the list of namespaces

    Do List^%SYS.NAMESPACE(.tList)

    Set tNS="" For  {

        Set tNS=$Order(tList(tNS),1,tValue) If tNS="" Quit

        #; Only want namespaces which are enabled and are not remote

        If $List(tValue,1)=1&&$List(tValue,2)=0 {

            Set tFilteredList(tNS)=""

        }

    }

    #; If we have been asked for json

    If $Get(%request.CgiEnvs("HTTP_ACCEPT"))="application/json" {

        #; Set the response header to JSON

        Set %response.ContentType="application/json"

        #; Create a JSON proxy

        set tProxy = {}

        ;Set tProxy = ##class(%ZEN.proxyObject).%New()

        #; And a list to hold the namespaces

        set tList= []

        ;Set tList=##class(%Library.ListOfDataTypes).%New()

        #; Add the namespaces to the list

        Set tNS="" For  {

            Set tNS=$Order(tFilteredList(tNS)) If tNS="" Quit

            do tList.$push(tNS)

            ;Do tList.Insert(tNS)

        }

        #; Set the namespace property

        Set tProxy.namespaces=tList

        #; Output the JSON

        set ^jks=tProxy.$toJSON()

        do tProxy.$toJSON()

        ;Do tProxy.%ToJSON()

    } else {

        Set tNS="" For  {

            Set tNS=$Order(tFilteredList(tNS)) If tNS="" Quit

            Write tNS,!

        }

    }

    Quit tSC

}

Unfortunately this returns an empty response when run. It LOOKS like both the original code do the same things but when I tested the original by setting a global equal to the value of tProxy.%ToJSON(), I got a 1 and the JSON sent twice in the response. When I set a global = tProxy.$toJSON() I actually get the JSON in the global. Is %ZEN.proxyObject.%ToJSON() doing something specific with the device that $toJSON() doesn't?