Add style/class to react-datepicker

So basicly how do I add a css class? I've given this a go but it ain't working:

<DatePicker 
       className="form-control 
       dateInput" 
       selected={startDate}  
       onChange={function(date){
                    startDate = date;
                 }
       }
/>

Thanks, Ed. (It's been compiled with webpack by the way.)