diff --git a/core/includes/theme.inc b/core/includes/theme.inc
index 5601b0f..fc4dcf6 100644
--- a/core/includes/theme.inc
+++ b/core/includes/theme.inc
@@ -2162,9 +2162,7 @@ function template_preprocess_field(&$variables, $hook) {
     $delta++;
   }
 
-  // Add default CSS classes. Since there can be many fields rendered on a page,
-  // save some overhead by calling strtr() directly instead of
-  // drupal_html_class().
+  // Creating variables for the template.
   $variables['entity_type'] = $element['#entity_type'];
   $variables['field_name'] = $element['#field_name'];
   $variables['field_type'] = $element['#field_type'];
diff --git a/core/modules/comment/templates/field--comment.html.twig b/core/modules/comment/templates/field--comment.html.twig
index 16d9009..413f339 100644
--- a/core/modules/comment/templates/field--comment.html.twig
+++ b/core/modules/comment/templates/field--comment.html.twig
@@ -23,16 +23,16 @@
  */
 #}
 {%
-  attributes.addClass([
+  set classes = [
     'field',
     'field-' ~ entity_type|clean_class ~ '--' ~ field_name|clean_class,
     'field-name-' ~ field_name|clean_class,
     'field-type-' ~ field_type|clean_class,
     'field-label-' ~ label_display,
-    'comment-wrapper'
-  ])
+    'comment-wrapper',
+  ]
 %}
-<section{{ attributes }}>
+<section{{ attributes.addClass(classes) }}>
   {% if comments and not label_hidden %}
     {{ title_prefix }}
     <h2{{ title_attributes.addClass('title') }}>{{ label }}</h2>
diff --git a/core/modules/node/templates/field--node--title.html.twig b/core/modules/node/templates/field--node--title.html.twig
index bb50423..4c7e434 100644
--- a/core/modules/node/templates/field--node--title.html.twig
+++ b/core/modules/node/templates/field--node--title.html.twig
@@ -16,12 +16,12 @@
  */
 #}
 {%
-  attributes.addClass([
+  set classes = [
     'field',
     'field-' ~ entity_type|clean_class ~ '--' ~ field_name|clean_class,
     'field-name-' ~ field_name|clean_class,
     'field-type-' ~ field_type|clean_class,
-    'field-label-' ~ label_display
-  ])
+    'field-label-' ~ label_display,
+  ]
 %}
-<span{{ attributes }}>{{ items }}</span>
+<span{{ attributes.addClass(classes) }}>{{ items }}</span>
diff --git a/core/modules/system/templates/field.html.twig b/core/modules/system/templates/field.html.twig
index 26dbfc2..e4093a0 100644
--- a/core/modules/system/templates/field.html.twig
+++ b/core/modules/system/templates/field.html.twig
@@ -33,25 +33,25 @@
  * @ingroup themeable
  */
 #}
-{%-
-  attributes.addClass([
+{%
+  set classes = [
     'field',
     'field-' ~ entity_type|clean_class ~ '--' ~ field_name|clean_class,
     'field-name-' ~ field_name|clean_class,
     'field-type-' ~ field_type|clean_class,
     'field-label-' ~ label_display,
-    label_display == 'inline' ? 'clearfix'
-  ])
--%}
-{%-
-  title_attributes.addClass([
+    label_display == 'inline' ? 'clearfix',
+  ]
+%}
+{%
+  set title_classes = [
     'field-label',
-    label_display == 'visually_hidden' ? 'visually-hidden'
-  ])
--%}
-<div{{ attributes }}>
+    label_display == 'visually_hidden' ? 'visually-hidden',
+  ]
+%}
+<div{{ attributes.addClass(classes) }}>
   {% if not label_hidden %}
-    <div{{ title_attributes }}>{{ label }}:&nbsp;</div>
+    <div{{ title_attributes.addClass(title_classes) }}>{{ label }}:&nbsp;</div>
   {% endif %}
   <div{{ content_attributes.addClass('field-items') }}>
     {% for delta, item in items %}
diff --git a/core/themes/bartik/templates/field--taxonomy-term-reference.html.twig b/core/themes/bartik/templates/field--taxonomy-term-reference.html.twig
index 14a86a8..84d66ee 100644
--- a/core/themes/bartik/templates/field--taxonomy-term-reference.html.twig
+++ b/core/themes/bartik/templates/field--taxonomy-term-reference.html.twig
@@ -16,26 +16,26 @@
  * @see bartik_preprocess_field()
  */
 #}
-{%-
-  attributes.addClass([
+{%
+  set classes = [
     'field',
     'field-' ~ entity_type|clean_class ~ '--' ~ field_name|clean_class,
     'field-name-' ~ field_name|clean_class,
     'field-type-' ~ field_type|clean_class,
     'field-label-' ~ label_display,
-    label_display == 'inline' ? 'clearfix'
-  ])
--%}
-{%-
-  title_classes.addClass([
+    label_display == 'inline' ? 'clearfix',
+  ]
+%}
+{%
+  set title_classes = [
     'field-label',
     label_display == 'inline' ? 'inline',
-    label_display == 'visually_hidden' ? 'visually-hidden'
-  ])
--%}
-<div{{ attributes }}>
+    label_display == 'visually_hidden' ? 'visually-hidden',
+  ]
+%}
+<div{{ attributes.addClass(classes) }}>
   {% if not label_hidden %}
-    <h3{{ title_attributes }}>{{ label }}: </h3>
+    <h3{{ title_attributes.addClass(title_classes) }}>{{ label }}: </h3>
   {% endif %}
   <ul{{ content_attributes.addClass('links', 'field-items') }}>
     {% for delta, item in items %}