Nested properties cannot be aggregated

Using ElasticSearch 6.4.1

"elasticsearch": "^15.1.1",
"graphql": "^14.0.2",
"graphql-compose": "^5.2.0",
"graphql-compose-elasticsearch": "^2.1.0",
"graphql-tools": "^4.0.3",

Live URL: [https://us-central1-production-197208.cloudfunctions.net/graphqlApiProd5?jwt=eyJhbGciOiJIUzI1NiJ9.eyJqdGkiOiJkY2Y1NWMzYjEwOGY0YWJjIiwiaWF0IjoxNTQxOTQ2OTU2LCJzdWIiOiJ1c2VyIiwiaXNzIjoiQXhvbml0ZSIsImJ1IjoiMTAwMDAwMDAwMDAwMDE0MiIsImlkIjoiMTAwMDAwMDAwMDAwMDE1MiIsInBhcnRuZXJzaGlwQ29udGV4dCI6Int9IiwiZXhwIjoxNTQ0NTM4OTU2fQ.XeCutA57k6tmv6q9SXPe4rGRfLthNikhOLQHuZNKysA](url)

This works:
`{
demandCampaign(query: {bool: {filter: {terms: {bu: ["652520790ac2952c"]}}}}, aggs: [{key: "subscription", value: {terms: {field: status}}}]) {
aggregations
}
}
`
This returns an error (works in Kibana, I believe the issue is with conversion of the __ to "." and back):
`{
demandCampaign(query: {bool: {filter: {terms: {bu: ["652520790ac2952c"]}}}}, aggs: [{key: "subscription", value: {terms: {field: demand__subscription}}}]) {
aggregations
}
}`