Rest API IsSubscribed filter not working

All,

I'm trying to set up an export of contacts that are unsubscribed from all campaigns. I set up an export definition using the following data, but every time I try to run it the data comes back with no results and the sync results in an error. I've tried multiple combinations to no avail.

Any help would be appreciated. I'm sure I'm missing something obvious...

{

   "name": "Unsubscribe Export",

   "fields": {

      "EmailAddress": "{{Contact.Field(C_EmailAddress)}}",

      "IsSubscribed": "{{Contact.Email.IsSubscribed}}"

   },

   "filter": "'{{Contact.Email.isSubscribed}}' = False"

}

Thanks!

Ben