API: posts.markdown missing from filters

[talflon]

posts.markdown is shown on the filter generation page, and a request with an empty filter (https://metasmoke.erwaysoftware.com/api/v2.0/posts/:id?filter=F) does return the markdown under the "markdown" key. But the filter generation fails to generate a filter that includes markdown, and I see that it's missing from api_field_mappings in config.sample.yml.

curl 'https://metasmoke.erwaysoftware.com/api/filters' -d 'fields=["posts.markdown"]'

returns

{"filter":"F"}