diff --git a/docs/snippets/advanced-directive-mixed.php b/docs/snippets/advanced-directive-mixed.php
index b2b6ad8..ffb3e7c 100644
--- a/docs/snippets/advanced-directive-mixed.php
+++ b/docs/snippets/advanced-directive-mixed.php
@@ -16,7 +16,7 @@ public function toArray(): array
             'foo' => 'bar',
 
             'some' => [
-                '@mixed' => <<<XML
+                '@mixed' => <<<'XML'
                     <first>value</first>
                     <second>value</second>
                     XML,