无法在自定义Elastic Beat中从fields.yml生成映射

I am currently writing a custom Beat using libbeat, and while I am able to build it, etc, and send data to my ElasticSearch cluster, I cannot get it to generate a real mapping based on the contents of fields.yml.

I have gone through every yml file involved, and they're all valid. When I run make update it is generating a correct, valid root-level fields.yml file. But no matter what I do, it is generating an empty mapping when I run export template.

- key: netbeat
  title: netbeat:
  fields:
    - name: snmp.host

Even this small amount isn't showing up.

I am receiving no errors at any point in the process, but it still is unable to generate a correct mapping. All I get is the default ILM-enabled mapping.