audio_tag does not generate correct path to assets in production. (Rails 3.2.2)

audio_tag_fix.rb

module ApplicationHelper
  def audio_tag(source, options = {})
    options.symbolize_keys!
    # originally defined as audio_path(source) but it doesn't work...
    options[:src] = path_to_asset(source)
    tag("audio", options)
  end
end