How to use custom sorter in XML views

I have the following list, using a custom sorter:

var oTemplate = ... // irrelevant

var oList = new sap.m.List({
    id: this.createId("someList"),
    items: {
        path: "/list",
        template: oTemplate,
        sorter: foo.bar.CustomSorter
    }
});

How can I use the custom sorter in XML views? Based on the answer at "Data-binding does not work in XML view", I tried following, but it didn't work:

<m:List id="someList"
        items="{
            path: '/list',
            sorter: 'foo.bar.CustomSorter'
        }">
    <!-- hid ListItem implementation -->
</m:List>

Removing the quotes around the sorter doesn't also work:

...
            sorter: foo.bar.CustomSorter
...