diff -u b/core/lib/Drupal/Component/DependencyInjection/Dumper/OptimizedPhpArrayDumper.php b/core/lib/Drupal/Component/DependencyInjection/Dumper/OptimizedPhpArrayDumper.php
--- b/core/lib/Drupal/Component/DependencyInjection/Dumper/OptimizedPhpArrayDumper.php
+++ b/core/lib/Drupal/Component/DependencyInjection/Dumper/OptimizedPhpArrayDumper.php
@@ -403,7 +403,7 @@
     elseif ($value instanceof Parameter) {
       return $this->getParameterCall((string) $value);
     }
-    elseif (preg_match('/^\%(.*)\%$/', $value, $matches)) {
+    elseif (is_string($value) && preg_match('/^\%(.*)\%$/', $value, $matches)) {
       return $this->getParameterCall($matches[1]);
     }
     elseif ($value instanceof Expression) {
diff -u b/core/tests/Drupal/Tests/Component/DependencyInjection/Dumper/OptimizedPhpArrayDumperTest.php b/core/tests/Drupal/Tests/Component/DependencyInjection/Dumper/OptimizedPhpArrayDumperTest.php
--- b/core/tests/Drupal/Tests/Component/DependencyInjection/Dumper/OptimizedPhpArrayDumperTest.php
+++ b/core/tests/Drupal/Tests/Component/DependencyInjection/Dumper/OptimizedPhpArrayDumperTest.php
@@ -147,7 +147,7 @@
 
       $parameter_bag = new ParameterBag($parameters);
       $this->containerBuilder->getParameterBag()->willReturn($parameter_bag);
-      $this->containerBuilder->isFrozen()->willReturn($is_frozen);
+      $this->containerBuilder->isCompiled()->willReturn($is_frozen);
 
       if (isset($parameters['reference'])) {
         $definition = new Definition('\stdClass');
diff -u b/core/tests/Drupal/Tests/Component/EventDispatcher/ContainerAwareEventDispatcherTest.php b/core/tests/Drupal/Tests/Component/EventDispatcher/ContainerAwareEventDispatcherTest.php
--- b/core/tests/Drupal/Tests/Component/EventDispatcher/ContainerAwareEventDispatcherTest.php
+++ b/core/tests/Drupal/Tests/Component/EventDispatcher/ContainerAwareEventDispatcherTest.php
@@ -195,49 +195,49 @@
     }
 
     /**
-     * @expectedDeprecation The Symfony\Component\EventDispatcher\ContainerAwareEventDispatcher class is deprecated since version 3.3 and will be removed in 4.0. Use EventDispatcher with closure factories instead.
+     * @expectedDeprecation The Symfony\Component\EventDispatcher\ContainerAwareEventDispatcher class is deprecated since Symfony 3.3 and will be removed in 4.0. Use EventDispatcher with closure factories instead.
      */
     public function testAddAListenerService() {
       parent::testAddAListenerService();
     }
 
     /**
-     * @expectedDeprecation The Symfony\Component\EventDispatcher\ContainerAwareEventDispatcher class is deprecated since version 3.3 and will be removed in 4.0. Use EventDispatcher with closure factories instead.
+     * @expectedDeprecation The Symfony\Component\EventDispatcher\ContainerAwareEventDispatcher class is deprecated since Symfony 3.3 and will be removed in 4.0. Use EventDispatcher with closure factories instead.
      */
     public function testPreventDuplicateListenerService() {
       parent::testPreventDuplicateListenerService();
     }
 
     /**
-     * @expectedDeprecation The Symfony\Component\EventDispatcher\ContainerAwareEventDispatcher class is deprecated since version 3.3 and will be removed in 4.0. Use EventDispatcher with closure factories instead.
+     * @expectedDeprecation The Symfony\Component\EventDispatcher\ContainerAwareEventDispatcher class is deprecated since Symfony 3.3 and will be removed in 4.0. Use EventDispatcher with closure factories instead.
      */
     public function testAddASubscriberService() {
       parent::testAddASubscriberService();
     }
 
     /**
-     * @expectedDeprecation The Symfony\Component\EventDispatcher\ContainerAwareEventDispatcher class is deprecated since version 3.3 and will be removed in 4.0. Use EventDispatcher with closure factories instead.
+     * @expectedDeprecation The Symfony\Component\EventDispatcher\ContainerAwareEventDispatcher class is deprecated since Symfony 3.3 and will be removed in 4.0. Use EventDispatcher with closure factories instead.
      */
     public function testHasListenersOnLazyLoad() {
       parent::testHasListenersOnLazyLoad();
     }
 
     /**
-     * @expectedDeprecation The Symfony\Component\EventDispatcher\ContainerAwareEventDispatcher class is deprecated since version 3.3 and will be removed in 4.0. Use EventDispatcher with closure factories instead.
+     * @expectedDeprecation The Symfony\Component\EventDispatcher\ContainerAwareEventDispatcher class is deprecated since Symfony 3.3 and will be removed in 4.0. Use EventDispatcher with closure factories instead.
      */
     public function testGetListenersOnLazyLoad() {
       parent::testGetListenersOnLazyLoad();
     }
 
     /**
-     * @expectedDeprecation The Symfony\Component\EventDispatcher\ContainerAwareEventDispatcher class is deprecated since version 3.3 and will be removed in 4.0. Use EventDispatcher with closure factories instead.
+     * @expectedDeprecation The Symfony\Component\EventDispatcher\ContainerAwareEventDispatcher class is deprecated since Symfony 3.3 and will be removed in 4.0. Use EventDispatcher with closure factories instead.
      */
     public function testRemoveAfterDispatch() {
       parent::testRemoveAfterDispatch();
     }
 
     /**
-     * @expectedDeprecation The Symfony\Component\EventDispatcher\ContainerAwareEventDispatcher class is deprecated since version 3.3 and will be removed in 4.0. Use EventDispatcher with closure factories instead.
+     * @expectedDeprecation The Symfony\Component\EventDispatcher\ContainerAwareEventDispatcher class is deprecated since Symfony 3.3 and will be removed in 4.0. Use EventDispatcher with closure factories instead.
      */
     public function testRemoveBeforeDispatch() {
       parent::testRemoveBeforeDispatch();
diff -u b/core/tests/Drupal/Tests/Listeners/DeprecationListenerTrait.php b/core/tests/Drupal/Tests/Listeners/DeprecationListenerTrait.php
--- b/core/tests/Drupal/Tests/Listeners/DeprecationListenerTrait.php
+++ b/core/tests/Drupal/Tests/Listeners/DeprecationListenerTrait.php
@@ -281,11 +281,12 @@
       "The 'rest.entity.workflow.GET.hal_json' route is deprecated since version 8.5.x and will be removed in 9.0.0. Use the 'rest.entity.workflow.GET' route instead.",
       'Using the unquoted scalar value "!php/object "O:8:\"stdClass\":1:{s:3:\"foo\";s:3:\"bar\";}"" is deprecated since version 3.3 and will be considered as a tagged value in 4.0. You must quote it.',
       'The Symfony\Component\ClassLoader\ApcClassLoader class is deprecated since Symfony 3.3 and will be removed in 4.0. Use `composer install --apcu-autoloader` instead.',
-      'Using the X-Status-Code header is deprecated since version 3.3 and will be removed in 4.0. Use Symfony\Component\HttpKernel\Event\GetResponseForExceptionEvent::allowCustomResponseCode() instead.',
-      'The Symfony\Component\EventDispatcher\ContainerAwareEventDispatcher class is deprecated since version 3.3 and will be removed in 4.0. Use EventDispatcher with closure factories instead.',
+      'Using the X-Status-Code header is deprecated since Symfony 3.3 and will be removed in 4.0. Use Symfony\Component\HttpKernel\Event\GetResponseForExceptionEvent::allowCustomResponseCode() instead.',
+      'The Symfony\Component\EventDispatcher\ContainerAwareEventDispatcher class is deprecated since Symfony 3.3 and will be removed in 4.0. Use EventDispatcher with closure factories instead.',
       'Not setting the strict option of the Choice constraint to true is deprecated since Symfony 3.4 and will throw an exception in 4.0.',
       'The Symfony\Component\HttpFoundation\Session\Storage\Handler\WriteCheckSessionHandler class is deprecated since Symfony 3.4 and will be removed in 4.0. Implement `SessionUpdateTimestampHandlerInterface` or extend `AbstractSessionHandler` instead.',
-      'Using the Yaml::PARSE_KEYS_AS_STRINGS flag is deprecated since Symfony 3.4 as it will be removed in 4.0. Quote your keys when they are evaluable instead.'
+      'Using the Yaml::PARSE_KEYS_AS_STRINGS flag is deprecated since Symfony 3.4 as it will be removed in 4.0. Quote your keys when they are evaluable instead.',
+      'The "session_handler.write_check" service relies on the deprecated "Symfony\Component\HttpFoundation\Session\Storage\Handler\WriteCheckSessionHandler" class. It should either be deprecated or its implementation upgraded.',
     ];
   }