diff --git a/core/lib/Drupal/Core/Template/TwigExtension.php b/core/lib/Drupal/Core/Template/TwigExtension.php
index 693da9a..0032770 100644
--- a/core/lib/Drupal/Core/Template/TwigExtension.php
+++ b/core/lib/Drupal/Core/Template/TwigExtension.php
@@ -497,6 +497,10 @@ public function renderVar($arg) {
       return NULL;
     }
 
+    if ($arg instanceof MarkupInterface) {
+      return $arg;
+    }
+
     // Optimize for scalars as it is likely they come from the escape filter.
     if (is_scalar($arg)) {
       return $arg;