Flexdashboard renderDataTable columns - no horizontal scroll


Hello, I have a renderDataTable object in a flexdashboard Shiny app and the header column doesn't scroll with the data across the bottom. Here's all of the code that I think controls the object. Thanks!

t <- datatable(t, extensions = 'Buttons',
                   options = list(scrollY = '300px', dom = 'Bfrtip',
                   buttons = c('csv'), paging = F), rownames = F)
    }, rownames = F)


Ugh, adding in scrollX = T fixes this issue. Nothing to see here. Thanks.