Extended Vuetify component doesn’t render

Stemming from the example in the Vuetify docs I am trying to extend a component and override a method.

Unlike the example, I am trying to extend VSelect:

<script lang="js">
    import Vue from 'vue'

    const VSelect = Vue.options.components["VSelect"]
    const ModifiedVSelect = {
        extends: VSelect
    }
</script>

I’ve started simple by not trying to override anything, but instead just extend the component and see if I can import it and use it in another component:

// lots of template stuff above
<div id="itemTypes">
  <ModifiedVSelect
    v-model="selectedTypes"
    :items="availableItems"
    label="Items"
    item-color="lightgrey"
    item-text="items"
    dense
    multiple
    return-object
  >
  </ModifiedVSelect>
</div>
// and more template stuff below

<script lang="js">
  import ModifiedVSelect from '../Controls/ModifiedVSelect'
  // other imports

  export default {
    name: 'MyComponent',
    components: {
      ModifiedVSelect,
      // other components
    },
  // bunch of other stuff
</script>

This v-select extension doesn’t render, but if I remove the import, registration and change the ModifiedVSelect to v-select in the <template></template>, then it renders.

Is there something else I need to do? Doesn’t appear to be outlined in the docs if so.