diff -u b/core/modules/views/src/Plugin/views/row/RssFields.php b/core/modules/views/src/Plugin/views/row/RssFields.php
--- b/core/modules/views/src/Plugin/views/row/RssFields.php
+++ b/core/modules/views/src/Plugin/views/row/RssFields.php
@@ -200,7 +200,8 @@
    *
    * @return string|null|\Drupal\Component\Render\MarkupInterface
    *   An empty string if there is no style plugin, or the field ID is empty.
-   *   And NULL if the field is actually empty otherwise MarkupInterface object.
+   *   NULL if the field value is empty. If neither of these conditions apply,
+   *   a MarkupInterface object containing the rendered field value.
    */
   public function getField($index, $field_id) {
     if (empty($this->view->style_plugin) || !is_object($this->view->style_plugin) || empty($field_id)) {