templateData variables return undefined from helper function (docpad.coffee configuration file)

This is my configuration file.

docpadConfig = {
    templateData:
        site:
            title: 'hello docpad'

        getTitle: ->
            @site.title

        getString: ->
            'just a string'
}

# Export the DocPad Configuration
module.exports = docpadConfig

From a jade layout when I do title= site.title it renders ok. When I try to call the helper function title= getTitle() the console outputs this:

error: An error occured:
ReferenceError: /Volumes/Data/project/am/lab/docpad/hello_docpad/src/layouts/default.html.jade:21
    19|
    20|     //- Our site title and description
  > 21|     title= getTitle()
    22|
    23|     //- Output DocPad produced meta elements
    24|     != getBlock('meta').toHTML()

site is not defined
    at docpadConfig.templateData.getWat (/Volumes/Data/project/am/lab/docpad/hello_docpad/docpad.coffee:10:16)
    at eval (eval at <anonymous> (/Volumes/Data/project/am/lab/docpad/hello_docpad/node_modules/docpad-plugin-jade/node_modules/jade/lib/jade.js:170:8), <anonymous>:47:64)

Looks like I can't access the site object from inside the helper function.

I'm sure I'm missing something trivial, maybe a plugin is needed for this... can't find out "wat" is wrong here.