CustomObject Data in DTO for AppCloud Apps

I was wondering if it was possible to get data from a CDO record mapped to the contact as part of the DTO that Eloqua sends to my Notification URL?

I tried to configure the DTO as:

{"recordDefinition":{

"CNA":"{{Contact.Field(C_CNA1)}}",

"ContactID":"{{Contact.Id}}",

"BonusPoint":"{{CustomObject[11].Field[379]}}",

"Email":"{{Contact.Field(C_EmailAddress)}}"}}

however, Eloqua throws and error 400 Bad Request.

If I leave out the line for the customobject field Eloqua accepts my DTO.

Am I using the wrong syntax or does Eloqua not support this (yet, hopefully)