Tagsinput bootstrap does not work

I'm using the bootstrap tags input in conjunction with Bootstrap 3 and I'm not getting the typehead to work. Code:

$('#tags').tagsinput();
   $('#tags').tagsinput({
       typeahead: {
       source: $.get('tags.php')
    }
});

tags.php return is

["Uruguaiana","Porto Alegre","Sao Paulo","Rio de Janeiro","Salvador"]

Does anyone know what the problem is?