diff --git a/core/lib/Drupal/Core/DrupalKernel.php b/core/lib/Drupal/Core/DrupalKernel.php
index 97650bd..9f8aaaa 100644
--- a/core/lib/Drupal/Core/DrupalKernel.php
+++ b/core/lib/Drupal/Core/DrupalKernel.php
@@ -250,12 +250,11 @@ public static function createFromRequest(Request $request, $class_loader, $envir
     // loader.
     if ($class_loader_class == get_class($class_loader)
         && Settings::get('class_loader_auto_detect', TRUE)
-        && Settings::get('hash_salt', FALSE)
         && function_exists('apc_fetch')) {
-      $apc_loader = new \Symfony\Component\ClassLoader\ApcClassLoader('drupal.' . Settings::get('hash_salt'), $class_loader);
+      $prefix = 'drupal' . hash('sha-256', 'drupal.' . Settings::getHashSalt());
+      $apc_loader = new \Symfony\Component\ClassLoader\ApcClassLoader($prefix, $class_loader);
       $class_loader->unregister();
       $apc_loader->register();
-      $class_loader = $apc_loader;
     }
 
     return $kernel;
diff --git a/core/rebuild.php b/core/rebuild.php
index 656673f..e89486f 100644
--- a/core/rebuild.php
+++ b/core/rebuild.php
@@ -22,7 +22,7 @@
 
 // Clear the APCu cache to ensure APCu classloader is reset.
 if (function_exists('apc_fetch')) {
-  apc_clear_cache();
+  apc_clear_cache('user');
 }
 
 $autoloader = require_once __DIR__ . '/vendor/autoload.php';
diff --git a/sites/default/default.settings.php b/sites/default/default.settings.php
index 4146ba2..152e3a9 100644
--- a/sites/default/default.settings.php
+++ b/sites/default/default.settings.php
@@ -403,7 +403,9 @@
  */
 /*
 if ($settings['hash_salt']) {
-  $apc_loader = new \Symfony\Component\ClassLoader\ApcClassLoader('drupal.' . $settings['hash_salt'], $class_loader);
+  $prefix = 'drupal.' . hash('sha-256', 'drupal' . $settings['hash_salt']);
+  $apc_loader = new \Symfony\Component\ClassLoader\ApcClassLoader($prefix, $class_loader);
+  unset($prefix);
   $class_loader->unregister();
   $apc_loader->register();
   $class_loader = $apc_loader;