diff --git a/core/lib/Drupal/Core/PhpStorage/PhpStorageFactory.php b/core/lib/Drupal/Core/PhpStorage/PhpStorageFactory.php
index 5ca0971..ccc8e3b 100644
--- a/core/lib/Drupal/Core/PhpStorage/PhpStorageFactory.php
+++ b/core/lib/Drupal/Core/PhpStorage/PhpStorageFactory.php
@@ -34,6 +34,7 @@ class PhpStorageFactory {
    *   An instantiated storage for the specified name.
    */
   static function get($name) {
+    $configuration = array();
     $overrides = Settings::get('php_storage');
     if (isset($overrides[$name])) {
       $configuration = $overrides[$name];
@@ -41,13 +42,12 @@ static function get($name) {
     elseif (isset($overrides['default'])) {
       $configuration = $overrides['default'];
     }
-    else {
-      $configuration = array(
-        'class' => 'Drupal\Component\PhpStorage\MTimeProtectedFileStorage',
-        'secret' => Settings::getHashSalt(),
-      );
-    }
-    $class = isset($configuration['class']) ? $configuration['class'] : 'Drupal\Component\PhpStorage\MTimeProtectedFileStorage';
+    // Merge in the minimally required default configuration.
+    $configuration += array(
+      'class' => 'Drupal\Component\PhpStorage\MTimeProtectedFileStorage',
+      'secret' => Settings::getHashSalt(),
+    );
+    $class = $configuration['class'];
     if (!isset($configuration['bin'])) {
       $configuration['bin'] = $name;
     }