CouchApp macro can't find file in _attachments directory

I'm trying to create a show function and use the !json macro to access some H开发者_JAVA技巧TML in a file in the _attachments directory of a standard CouchApp.

However when I try and push the CouchApp, it says

MacroError: Processing code: No file matching '_attachments.foo'

where foo.html is what I'm trying to access.

It can find the file if I move foo.html to the top of the directory structure, but I don't want to do that.