Action Attribute on lightning:tabset

Hello people,

can someone help me, with the following problem.
I have following code in my Lightning component

<lightning:tabset >
    <aura:iteration items="{!v.Items}" var="item">
        <lightning:tab label="{!item}" onactive="{!c.tabClick}">
            <ui:outputtext value="{!item}" />
        </lightning:tab>
    </aura:iteration>
</lightning:tabset>

The problem is the "onactive" attribute of the lightning:tab, Salesforce says:

Failed to save undefined: The attribute "onactive" was not found on the COMPONENT markup://lightning:tab: Source

But the sfdc documentation states, that the attribute exists
https://developer.salesforce.com/docs/atlas.en-us.lightning.meta/lightning/aura_compref_lightning_tab.htm?search_text=lightning:tab

Is it, because tabs are still beta or have I done something wrong?

The Lightning inspector shows me this when I save without onactive:
<lightning:tab onfocus="null" onblur="null"