Sonata Admin List Field Template is Ignored

I'm using Symfony 4.1.1 and Sonata Admin Bundle 3.35.2.

I want to use a custom template for a field in an admin's list view. The template is ignored. I am using Twig as my templating engine.

In the admin:

# /src/Admin/ImageAdmin.phpprotected function configureListFields(ListMapper $listMapper) {    $listMapper        ->add('filename', 'string', ['template' => 'list_image.html.twig'])    ;}

The template:

# /templates/list_image.html.twig{% extends 'SonataAdminBundle:CRUD:base_list_field.html.twig' %}{% block field %}<img src="{{ value }}" style="width: 200px" />{% endblock %}