Ember data "Assertion Failed: Attributes must be numbers, [...], not function (data) { return template [...]"

I have this error from time to time when I transition from one route to another :

Uncaught Error: Assertion Failed: Attributes must be numbers, strings or booleans, not function (data) {
  return template
    .replace(/\{\{\{\s*(.*?)\s*\}\}\}/g, function(i, match) {
      // tripple curlies -> no-escaping
      return get(data, match);
    }).replace(/\{\{\s*(.*?)\s*\}\}/g, function(i, match) {
     return escapeExpression( get(data, match) );
    });
}

I'm using "ember-cli": "0.2.5", "ember-data": "1.0.0-beta.19" and "ember": "1.12.0".

I don't have a clue where that could come from, any lead please ?