diff --git a/modules/promotion/commerce_promotion.post_update.php b/modules/promotion/commerce_promotion.post_update.php
index 7042d7d6bc..699d127060 100644
--- a/modules/promotion/commerce_promotion.post_update.php
+++ b/modules/promotion/commerce_promotion.post_update.php
@@ -233,3 +233,57 @@ function commerce_promotion_post_update_8(&$sandbox = NULL) {
     $sandbox['#finished'] = ($sandbox['total_count'] - $sandbox['current_count']) / $sandbox['total_count'];
   }
 }
+
+/**
+ * Change the description basefield to support formatted text.
+ */
+function commerce_promotion_post_update_9() {
+  // To update the field schema we need to have no field data in the storage,
+  // thus we retrieve it, delete it from storage, and write it back to the
+  // storage after updating the schema.
+  $database = \Drupal::database();
+
+  // Check update is needed.
+  if ($database->schema()->fieldExists('commerce_promotion_field_data', 'description')) {
+    // Retrieve existing field data.
+    $descriptions = $database->select('commerce_promotion_field_data', 'cp')
+      ->fields('cp', ['promotion_id', 'description'])
+      ->execute()
+      ->fetchAllKeyed();
+
+    // Remove data from the storage.
+    $database->update('commerce_promotion_field_data')
+      ->fields(['description' => NULL])
+      ->execute();
+
+    // Update definitions and schema.
+    $entity_definition_manager = \Drupal::entityDefinitionUpdateManager();
+    /** @var Drupal\Core\Field\BaseFieldDefinition $storage_definition */
+    $storage_definition = $entity_definition_manager->getFieldStorageDefinition('description', 'commerce_promotion');
+    $entity_definition_manager->uninstallFieldStorageDefinition($storage_definition);
+
+    $storage_definition = BaseFieldDefinition::create('text_long')
+      ->setLabel(t('Description'))
+      ->setDescription(t('Additional information about the promotion to show to the customer'))
+      ->setTranslatable(TRUE)
+      ->setDefaultValue('')
+      ->setDisplayOptions('form', [
+        'type' => 'text_textarea',
+        'weight' => 1,
+        'settings' => [
+          'rows' => 3,
+        ],
+      ])
+      ->setDisplayConfigurable('view', TRUE)
+      ->setDisplayConfigurable('form', TRUE);
+    $entity_definition_manager->installFieldStorageDefinition('description', 'commerce_promotion', 'commerce_promotion', $storage_definition);
+
+    // Restore entity data in the new schema.
+    foreach ($descriptions as $promotion_id => $description) {
+      $database->update('commerce_promotion_field_data')
+        ->fields(['description__value' => $description])
+        ->condition('promotion_id', $promotion_id)
+        ->execute();
+    }
+  }
+}
diff --git a/modules/promotion/src/Entity/Promotion.php b/modules/promotion/src/Entity/Promotion.php
index 52842cea0d..6876cf0425 100644
--- a/modules/promotion/src/Entity/Promotion.php
+++ b/modules/promotion/src/Entity/Promotion.php
@@ -545,13 +545,13 @@ public static function baseFieldDefinitions(EntityTypeInterface $entity_type) {
       ->setDisplayConfigurable('view', TRUE)
       ->setDisplayConfigurable('form', TRUE);
 
-    $fields['description'] = BaseFieldDefinition::create('string_long')
+    $fields['description'] = BaseFieldDefinition::create('text_long')
       ->setLabel(t('Description'))
       ->setDescription(t('Additional information about the promotion to show to the customer'))
       ->setTranslatable(TRUE)
       ->setDefaultValue('')
       ->setDisplayOptions('form', [
-        'type' => 'string_textarea',
+        'type' => 'text_textarea',
         'weight' => 1,
         'settings' => [
           'rows' => 3,