diff --git a/core/modules/filter/src/Plugin/Filter/FilterCaption.php b/core/modules/filter/src/Plugin/Filter/FilterCaption.php
index ed241d8..97f6f21 100644
--- a/core/modules/filter/src/Plugin/Filter/FilterCaption.php
+++ b/core/modules/filter/src/Plugin/Filter/FilterCaption.php
@@ -13,6 +13,7 @@
 use Drupal\Component\Utility\Xss;
 use Drupal\filter\FilterProcessResult;
 use Drupal\filter\Plugin\FilterBase;
+use Drupal\Core\Render\SafeString;
 
 /**
  * Provides a filter to caption elements.
@@ -59,7 +60,7 @@ public function process($text, $langcode) {
         $node->removeAttribute('class');
         $filter_caption = array(
           '#theme' => 'filter_caption',
-          '#node' => SafeMarkup::set($node->C14N()),
+          '#node' => SafeString::create($node->C14n()),
           '#tag' => $node->tagName,
           '#caption' => $caption,
           '#classes' => $classes,