Fixed columns and fixed header - can't scroll columns horizontally.

zaw

I'm using FixedColumns and FixedHeader extensions.
I fixed first two columns by using fixedColumns extension and fixed header by using fixedHeader extension.
When fixedHeader is working, horizontal scroll is not working.
It should be able to scroll columns except two fixed columns

https://cloud.githubusercontent.com/assets/5483800/15284238/2f14e47c-1b76-11e6-82a3-168004b2e9b0.PNG

My js code is the following:
var table = $('#data-table').DataTable({
// scrollY : 300,
scrollX : true,
scrollCollapse : true,
paging : true,
fixedColumns : {
leftColumns: 2
},
fixedHeader : {
headerOffset: $('#header').outerHeight()
}
});

Thank you for your help.