Tip of the hat to Zerot in FreeNode's #angularjs
app.config(['$routeProvider', '$httpProvider', function($routeProvider, $httpProvider) {
$httpProvider.defaults.headers.common['X-Requested-With'] = 'XMLHttpRequest';
$routeProvider.when('/', {
templateUrl: '/path/on/server',
controller: 'Ctrl'
});
});
Edit: to be more specific, this is the line you need somewhere:
$httpProvider.defaults.headers.common['X-Requested-With'] = 'XMLHttpRequest';