Dialog Scroll

Hi I am trying to make a dialog with button content. If the content is big then the dialog doesn't scroll even if I set a maxHeight. The dialog overlaps the screen.
What do I need to do?

<Dialog
        id="MonthDialog"
        title="SELECT A MONTH"
        iconUri=""
        maxHeight="300"
        optionsDialog="true"
        visible="false"/>
Buttons = ["asd","asd","asd","asd","asd","asd","asd","asd","January", "February", "March", "April", "May", "June", "July", "August", "September", "October", "November", "December"]
m.top.dialog.buttons = buttons

What do