diff --git a/core/modules/rdf/rdf.module b/core/modules/rdf/rdf.module
index 35ac8b8..d9ac910 100644
--- a/core/modules/rdf/rdf.module
+++ b/core/modules/rdf/rdf.module
@@ -446,16 +446,18 @@ function rdf_preprocess_comment(&$variables) {
     $author_attributes = ['rel' => $author_mapping['properties']];
     // Wraps the 'author' and 'submitted' variables which are both available in
     // comment.html.twig.
-    $variables['author'] = [
+    $author = [
       '#theme' => 'rdf_wrapper',
       '#content' => $variables['author'],
       '#attributes' => $author_attributes,
     ];
-    $variables['submitted'] = [
+    $submitted = [
       '#theme' => 'rdf_wrapper',
       '#content' => $variables['submitted'],
       '#attributes' => $author_attributes,
     ];
+    $variables['author'] = SafeMarkup::checkPlain(drupal_render($author));
+    $variables['submitted'] = SafeMarkup::checkPlain(drupal_render($submitted));
   }
   // Adds RDFa markup for the date of the comment.
   $created_mapping = $mapping->getPreparedFieldMapping('created');
@@ -472,8 +474,10 @@ function rdf_preprocess_comment(&$variables) {
     $created = !is_array($variables['created']) ? ['#markup' => $variables['created']] : $variables['created'];
     $submitted = !is_array($variables['submitted']) ? ['#markup' => $variables['submitted']] : $variables['submitted'];
     // Make render array and RDF metadata available in comment.html.twig.
-    $variables['created'] = [$created, $rdf_metadata];
-    $variables['submitted'] = [$submitted, $rdf_metadata];
+    $created_render = [$created, $rdf_metadata];
+    $submitted_render = [$submitted, $rdf_metadata];
+    $variables['created'] = SafeMarkup::checkPlain(drupal_render($created_render));
+    $variables['submitted'] = SafeMarkup::checkPlain(drupal_render($submitted_render));
   }
   $title_mapping = $mapping->getPreparedFieldMapping('subject');
   if (!empty($title_mapping)) {