diff --git a/includes/listing.inc b/includes/listing.inc
new file mode 100644
index 000000000..bdd188e57
--- /dev/null
+++ b/includes/listing.inc
@@ -0,0 +1,26 @@
+<?php
+
+/**
+ * @file
+ * Theme and preprocess functions for Pattern listing.
+ */
+
+declare(strict_types = 1);
+
+/**
+ * Implements hook_preprocess_HOOK().
+ */
+function oe_bootstrap_theme_preprocess_pattern_listing(array &$variables) {
+  if (!empty($variables['items'])) {
+    foreach ($variables['items'] as &$item) {
+      if (!empty($item['content']['#theme'])) {
+        $id = $item['content']['#theme'];
+        if (!empty($item['content']['#'. $id])) {
+          /** @var Drupal\Core\Entity\ $entity */
+          $entity = $item['content']['#'. $id];
+          $variables['attributes']->addClass($entity->bundle());
+        }
+      }
+    }
+  }
+}