diff --git a/core/modules/views/src/Plugin/views/row/OpmlFields.php b/core/modules/views/src/Plugin/views/row/OpmlFields.php
index 4654bcad724ffb614792e907902b22a8764ce0db..a2ddf436792b77a9a98f399e007339e4d4d07cc1 100644
--- a/core/modules/views/src/Plugin/views/row/OpmlFields.php
+++ b/core/modules/views/src/Plugin/views/row/OpmlFields.php
@@ -212,6 +212,9 @@ public function render($row) {
    *   The index count of the row as expected by views_plugin_style::getField().
    * @param $field_id
    *   The ID assigned to the required field in the display.
+   *
+   * @return string
+   *   The rendered field value.
    */
   public function getField($index, $field_id) {
     if (empty($this->view->style_plugin) || !is_object($this->view->style_plugin) || empty($field_id)) {
diff --git a/core/modules/views/src/Plugin/views/row/RssFields.php b/core/modules/views/src/Plugin/views/row/RssFields.php
index 5fa91cc672a053fa5362f05105a3bf54d0e694d0..b35172ae3411c2f1f4d6bd895d56767523cb7b23 100644
--- a/core/modules/views/src/Plugin/views/row/RssFields.php
+++ b/core/modules/views/src/Plugin/views/row/RssFields.php
@@ -199,6 +199,11 @@ public function render($row) {
    *   The index count of the row as expected by views_plugin_style::getField().
    * @param $field_id
    *   The ID assigned to the required field in the display.
+   *
+   * @return string|null|\Drupal\Component\Render\MarkupInterface
+   *   An empty string if there is no style plugin, or the field ID is empty.
+   *   NULL if the field value is empty. If neither of these conditions apply,
+   *   a MarkupInterface object containing the rendered field value.
    */
   public function getField($index, $field_id) {
     if (empty($this->view->style_plugin) || !is_object($this->view->style_plugin) || empty($field_id)) {