diff -u b/core/lib/Drupal/Core/DrupalKernel.php b/core/lib/Drupal/Core/DrupalKernel.php
--- b/core/lib/Drupal/Core/DrupalKernel.php
+++ b/core/lib/Drupal/Core/DrupalKernel.php
@@ -333,7 +333,7 @@
     $persist = array();
     if (isset($this->container)) {
       foreach ($this->container->getParameter('persistIds') as $id) {
-        // Only persist services that have already been instantiated.
+        // It's pointless to persist services not yet initialized.
         if ($this->container->initialized($id)) {
           $persist[$id] = $this->container->get($id);
         }
@@ -347,8 +347,8 @@
    */
   protected function persistServices(array $persist) {
     foreach ($persist as $id => $object) {
-      // Do not override services explicitly instantiated on the new container
-      // prior to the invocation of this function.
+      // Do not override services already set() on the new container, for
+      // example 'service_container'.
       if (!$this->container->initialized($id)) {
         $this->container->set($id, $object);
       }