diff --git a/core/lib/Drupal/Core/DrupalKernel.php b/core/lib/Drupal/Core/DrupalKernel.php
index e1842fc..3df5fdd 100644
--- a/core/lib/Drupal/Core/DrupalKernel.php
+++ b/core/lib/Drupal/Core/DrupalKernel.php
@@ -250,6 +250,7 @@ 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')) {
       $prefix = 'drupal.' . hash('sha-256', 'drupal.' . Settings::getHashSalt());
       $apc_loader = new \Symfony\Component\ClassLoader\ApcClassLoader($prefix, $class_loader);
diff --git a/core/rebuild.php b/core/rebuild.php
index 78d4fce..05e384e 100644
--- a/core/rebuild.php
+++ b/core/rebuild.php
@@ -20,7 +20,7 @@
 // Change the directory to the Drupal root.
 chdir('..');
 
-// APC user cache to ensure APC classloader is reset.
+// Clear the APC user cache to ensure APC class loader is reset.
 if (function_exists('apc_fetch')) {
   apc_clear_cache('user');
 }