ember-cli-htmlbars plugins not processing in-repo addon templates

I'm using a plugin for ember-cli-htmlbars in an addon to process the template ASTs. It works correctly for templates in my addon's dummy application.

However, the dummy application has an in-repo addon that contains templates in addon/templates/. The in-repo addon specifies ember-cli-htmlbars inside of its package.json, which causes the templates to compile correctly -- with the exception of not being passed through the plugin I have registered in the parent addon. The end result is that in-repo addon templates are not being processed by my plugin, which is ultimately fatal to my addon at runtime.

How can I cause the in-repo addon's templates to also be processed using the ember-cli-htmlbars plugin I specified in my addon?