Cannot import Nuxeo.ChartDataBehavior

I am trying to build some analytics and not reinventing the wheel, so I wanted to import the behavior:

. . .
  <script>
    Polymer({
      is: 'retention-analytics',
      behaviors: [Nuxeo.ChartDataBehavior, Nuxeo.I18nBehavior],
. . .

This fails at runtime, the console says it cannot find the behavior:

behavior is null, check for missing or 404 import

When digging with Guillaume, the error is throw in Nuxeo-app.htmp#10287

error: This behavior being vulcanized it should be available.
Workaround: Duplicate/rename the behavior file, or just copy/paste the function used in the custom charts