sizePerPageDropDown not working in IE 11

I am using react-bootstrap-table 4.0.1, IE 11.0.9600.18762, bootstrap 3.3.7.

When I use the sizePerPageDropDown option and create my own sizePerPageDropDown control, it works fine in Chrome, but for IE 11 it seems to ignore this option completely. My sizePerPageDropDown render function creates a drop down box with the values 10, 20, 30, 40, 50. I see this fine in Chrome. However, when rendering in IE it shows the default 10, 25, 30, 50 and doesn't render anything in my function for sizePerPageDropDown. My code is below:

renderSizePerPageDropDown(props) {
const sizes = [10, 20, 30, 40, 50]
const sizePerPageOptions = sizes.map(sizeItem => {sizeItem})
return (

render() {
....

const options = {
sizePerPage: 20,
sizePerPageDropDown: this.renderSizePerPageDropDown,
}
const TableHeaderColumns =[an array of TableHeaderColumn]

return (
{ this.tableRef = tableRef }}
data={data}
options={options}
tableStyle={{ border: "none" }}
condensed
striped
pagination
>
{TableHeaderColumns}

)
}

Any idea why this doesn't work in IE 11?