So I've created a small subtheme called bartik_graphql. It just overrides the 'Powered by Drupal' block. Besides it's bartik_graphql.info.yml file it has a templates directory containing one file block--bartik-graphql-powered.html.twig.

Contents of block--bartik-graphql-powered.html.twig:

query {
  admin:userById(id: "1") {

{% extends "@bartik/block" %}

{% block content %}
  <div{{ content_attributes.addClass('content') }}>
    {{ content }} and some guy named {{ graphql.data.admin.name }}
{% endblock %}

I've enabled my subtheme and set it to default. However I receive the following error:

Twig\Error\LoaderError: Template "@bartik/block" is not defined. in Twig\Loader\ChainLoader->getCacheKey() (line 122 of web/core/themes/bartik/templates/page.html.twig).

What I expect to happen is have my subtheme's template override what is used by default to display the 'Powered by Drupal' message.

Drupal: 8.7.8
PHP: 7.2.17

Am I using extends wrong here?

1 Answer 1


I didn't know of Twig namespacing just until now. But what always worked for extends and includes is to point to the template you want to extend/include directly, with the path starting from Drupal web root. So in your case it needs to say:

{% extends "core/themes/bartik/templates/block.html.twig" %}

You could also try the following which seems to follow theme inheritance but only up to the final base theme (which would be Classy).

{% extends "@block/block.html.twig" %}
  • 1
    Thanks @leymannx that has appeared to do the trick. In my searches to find a solution I found similar suggestions but the particular example I was looking at on YouTube showed him successfully using {% extends @bartik/block" %}. Could that perhaps be that the tutorial was from mid-2018 and that's no longer how it's done?
    – frmt
    Oct 14, 2019 at 20:35
  • 1
    @frmt – Oh wow, I've never recognized Twig namespacing is actually used in a few places even in core. I just tried the same but for me it also doesn't work. Whereas Drupal root-relative paths work just fine...
    – leymannx
    Oct 14, 2019 at 20:51
  • It's even in the documentation in places like GraphQL Twig. I posted in their Slack channel about it, hopefully I can gain some more insight as to what they are doing.
    – frmt
    Oct 14, 2019 at 21:03
  • 1
    Will do. Once I get back in the office in the morning I'll try that out and update you. There is a similar issue I'm having related to the same webinar on GraphQL Twig, so I also commented on that issue. It hasn't been addressed in three months so hopefully pinging it again will bring it to the forefront again.
    – frmt
    Oct 15, 2019 at 0:08
  • 2
    Here is an update @leymannx. @block/block.html.twig works too, although the resulting output is minimal, I'm assuming Classy is pretty bare bones. When using your original suggestion I get a lot of stuff inherited from Bartik.
    – frmt
    Oct 15, 2019 at 16:12

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