AngularJS: angular-drag-and-drop-lists dnd-allowed-types not evaluating to true for matching dnd-type

I am currently using angular-drag-and-drop-lists to generate a JsonDTO Object. Generating the graphical representation from a JSON works fine. And generating a JSON by dragging and dropping the different elements works fine as well. I mainly used the nested list tutorial to set up the initial list and setting up the buttons to drag new elements from. However this only works until I try to add dnd-type to the li-elements and dnd-allowed-type to the ul-elements. Using those types is a requirements, as there is a certain hierarchical structure of subelements in the Json I want to create with that 'editor'.

Find below some code snippets how I implemented it. If you need further information let me know. I would really appreciate if anyone could help me with this issue

THe list I want to inset something into:

<div class="form-group label-floating">
    <label class="control-label" for="name">Name</label>
    <input class="form-control" type="text" class="form-control" id="name"  ng-model="models.questionnaire.name">
</div>
<ul dnd-list="models.questionnaire.pages"
    dnd-allowed-types="models.allowedTypes.questionnaire">
    <li ng-repeat="page in models.questionnaire.pages"
        dnd-draggable="page"
        dnd-type="page.type"
        dnd-effect-allowed="move"
        dnd-moved="models.questionnaire.pages.splice($index, 1)"
        dnd-selected="models.selected = page"
        ng-class="{'selected': models.selected === page}"
        ng-include="'page.html'">
    </li>
</ul>

The button to drag a new page from:

<li dnd-draggable="{title: 'title', dndType: 'page', sections: []}"
            dnd-effect-allowed="copy">
            <button type="button" class="btn btn-default btn-lg" disabled="disabled">Page</button>
        </li>

In case anyone has the same question, that is my solution for the button to drag the page from:

<li dnd-draggable="{title: 'title', sections: []}"
            dnd-effect-allowed="copy"
            dnd-type="'page'">
            <button type="button" class="btn btn-default btn-lg" disabled="disabled">Page</button>

        </li>

In my case I forgot to set the dnd-type, as it was not used in the example code I looked at.