deploy rails + ember oh heroku: Uncaught Error: Could not find module `dashboard/app` imported from `(require)`

Deploying Rails + Ember application first time on Heroku. In development it's fine but in production it throw an error

Uncaught Error: Could not find module `dashboard/app` imported from `(require)`

Where dashboard is an ember app. I'm using ember-cli-rails rails and following setting-up-emberjs-with-rails-ember-cli-edition But no luck.

Dashboard directory is parallel to main rails app

package.json

{
  "engines": {
    "node": "0.12.4"
  },
  "scripts": {
    "postinstall": "./bin/heroku_install"
  },
  "devDependencies": {
    "bower": "*"
  },
  "cacheDirectories": [
    "dashboard/node_modules",
    "dashboard/bower_components",
    "node_modules"
  ]
}

ember.rb

EmberCli.configure do |config|
  config.app :dashboard
end

Let me know if any one need other info as well.

Any help would be appreciated !!!