Mutiple views in one tab

I found the answer to my own question!
It's a routing mistake...
To do this, the tabs.details state must have the same view name as the parent tab.

.state('tabs.news', {
    url: '/news',
    views: {
        'news-tab': {
            templateUrl: 'templates/news.html',
            controller: 'NewsCtrl'
        }
    }
})
.state('tabs.details', {
    url: '/details',
    views: {
        'news-tab': { // SAME VIEW NAME!!!
            templateUrl: 'templates/details.html',
            controller: 'DetailsCtrl'
        }
    }
})