Ripples on a shape with a transparent background

After a few trial and errors it seems I have misunderstood the hierarchy of the selector and item.

The following works perfectly.

<ripple xmlns:android="http://schemas.android.com/apk/res/android"
        android:color="@color/primary_light">
        <item android:id="@android:id/mask">
               <shape android:shape="oval">
                       <solid android:color="@android:color/white"/>
                       <size android:height="80dp" android:width="80dp"/>
               </shape>
        </item>
</ripple>