diff --git a/core/lib/Drupal/Component/Yaml/Yaml.php b/core/lib/Drupal/Component/Yaml/Yaml.php
index ee759b2..a632416 100644
--- a/core/lib/Drupal/Component/Yaml/Yaml.php
+++ b/core/lib/Drupal/Component/Yaml/Yaml.php
@@ -66,8 +66,9 @@ protected function determineImplementation() {
       return static::$implementationClass;
     }
 
+    $settings = Settings::getSingleton();
     // If there's a settings.php override, use that.
-    if ($class = Settings::getSingleton()->get('yaml_parser_class')) {
+    if ($settings && ($class = $settings->get('yaml_parser_class'))) {
       static::$implementationClass = $class;
     }
     // If the PECL YAML extension installed, use that.