diff --git a/core/lib/Drupal/Core/Serialization/Yaml.php b/core/lib/Drupal/Core/Serialization/Yaml.php
index 6e7b37cf7a8d5ead6065f8463c922acb2890fb96..b17b57302b91f5879e83b06196900f6fbc25c2b6 100644
--- a/core/lib/Drupal/Core/Serialization/Yaml.php
+++ b/core/lib/Drupal/Core/Serialization/Yaml.php
@@ -13,7 +13,8 @@
 class Yaml extends ComponentYaml {
 
   public static function decode($raw) {
-    if ($class = Settings::get('yaml_parser_class')) {
+    $class = Settings::get('yaml_parser_class');
+    if ($class && $class !== TRUE) {
       return $class::decode($raw);
     }