Server side processing not honoring fixedColumns

dshine

My data code looks like this

        $(document).ready(function () {
            $('#myTable').DataTable({
                fixedHeader: true,
                ordering: false,
                pageLength: 50,
                searching: true,
                searchDelay: 1000,
                processing: true,
                serverSide: true,
                scrollY: calcDataTableHeight(),
                scrollX: true,
                ajax : {
                    url : '/my/url',
                    type : 'POST'
                },
                columns: [
                    {
                           // column defs here
                ],
                fixedColumns: {
                    leftColumns: 1
                }
            });
        });

However, when I scroll to the right the left most column still disappears. What am I doing wrong?