With the Winter'18 new Lightning Base components I tried to create a `lightning:progressIndicator` with `lightning:progressStep` dynamically using  an `aura:iteration`:

    <aura:component>
        <lightning:progressIndicator currentStep="{!stage.id}">
            <aura:iteration items="{!v.stages}" var="stage">
                <lightning:progressStep label="{!stage.label}" value="{!stage.id}"/>
            </aura:iteration>
        </lightning:progressIndicator>
    </aura:component>

The page throws strange errors like:

> Uncaught Action failed: aura:iteration$controller$itemsChange [Cannot
> read property 'hasOwnProperty' of undefined]

[![enter image description here][1]][1]


  [1]: https://i.sstatic.net/J1ZE1h.png