metadata override in README.md is being ignored

[papadeltasierra]

Ref: docs/metadata.md

I am working with XML in a README.md file that looks like this:

``` yaml
require:
  - some/path/to/file.md

metadata:
  authors: The Author I Want

The file /some/path/to/file.md contains the following:

> Values
``` yaml
metadata:
  authors: Some other Author

I am finding that my attempt to override the author is being ignored - is this expected? Is there any way to make my override take affect?