Error using native node.js

I have `sbt-rjs` working to optimize my js, and it seems pretty great!  However, the JVM implementation is very slow, as you mentioned, so I am trying to switch to the native node implementation.  I tried adding this to my `build.sbt` file:

    JsEngineKeys.engineType := JsEngineKeys.EngineType.Node

However, I get this error when I run `stage`:

    [info] Error: Error: Build file /Users/pkaeding/prj/gmaps-play/target/web/rjs/app.build.js is malformed: SyntaxError: Duplicate data property in object literal not allowed in strict mode
    [info]     at Function.build.createConfig (/Users/pkaeding/prj/gmaps-play/project/target/node-modules/webjars/requirejs/bin/r.js:26708:23)

This is with the same `app.build.js` file that works under the Trireme implementation.  I added some logging to my `app.build.js` so that it logs the object it returns, and I then put that config (with all the paths filled in) into an `app.build2.js` file, and I can successfully run `r.js` natively using that config.

Is there anything else I need to do to enable the native node support?  I couldn't find much documentation on the web.