diff --git a/core/modules/taxonomy/taxonomy.module b/core/modules/taxonomy/taxonomy.module
index d58064d..bd53bba 100644
--- a/core/modules/taxonomy/taxonomy.module
+++ b/core/modules/taxonomy/taxonomy.module
@@ -320,10 +320,7 @@ function template_preprocess_taxonomy_term(&$variables) {
     $variables['content'][$key] = $variables['elements'][$key];
   }
 
-  // Gather classes, and clean up name so there are no underscores.
-  $variables['attributes']['class'][] = 'taxonomy-term';
-  $vocabulary_name_css = str_replace('_', '-', $term->bundle());
-  $variables['attributes']['class'][] = 'vocabulary-' . $vocabulary_name_css;
+  $variables['vocabulary_name'] = $term->bundle();
 }
 
 /**
diff --git a/core/modules/taxonomy/templates/taxonomy-term.html.twig b/core/modules/taxonomy/templates/taxonomy-term.html.twig
index 2ecc713..dce03e0 100644
--- a/core/modules/taxonomy/templates/taxonomy-term.html.twig
+++ b/core/modules/taxonomy/templates/taxonomy-term.html.twig
@@ -29,7 +29,13 @@
  * @ingroup themeable
  */
 #}
-<div id="taxonomy-term-{{ term.id }}"{{ attributes }}>
+{%
+  set classes = [
+    'taxonomy-term',
+    'vocabulary-' ~ vocabulary_name|clean_class,
+  ]
+%}
+<div id="taxonomy-term-{{ term.id }}"{{ attributes.addClass(classes) }}>
   {{ title_prefix }}
   {% if not page %}
     <h2><a href="{{ url }}">{{ name }}</a></h2>