Ajax responseChanged return logged twice

[alitavector]

From the chrome dev tool, it seem to log output the "test" message twice each times the submit button is press.

...
<core-ajax id="ajax" method="POST" url="r.php" params="{{item}}" response="{{response}}"></core-ajax>
    <template repeat="{{response}}">{{data}}</template>
    {{response}}
    <br>
  </template>
  <script>
    Polymer('add-node', {
      created: function() {
        this.item = {};
      },
      doSend: function() {
        this.$.ajax.go();
      },
      responseChanged: function() {
        console.log("test");
      }
    });
  </script>

[ebidel]

This issue was moved to googlearchive/core-ajax#43