Unknown "bt" filter

[redburn]

src/templates/_includes/macros.twig

{% macro configWarning(setting) %}
    {% set setting = '<code>'~setting~'</code>' %}
    {{ "This setting is being overridden by {setting} in the {file} config file."|bt({
        setting: setting,
        file: '<code>slugsmith.php</code>'
    })|raw }}
{% endmacro %}

That bt() should probably be t()?

Currently throwing:
Twig Syntax Error – Twig\Error\SyntaxError
Unknown "bt" filter.

On the Settings page.

Love the idea of the slug refresh button, by the way.