diff -u b/core/core.services.yml b/core/core.services.yml
--- b/core/core.services.yml
+++ b/core/core.services.yml
@@ -471,8 +471,7 @@
     arguments: ['@app.root', '@module_handler', '@cache.discovery']
   theme.negotiator:
     class: Drupal\Core\Theme\ThemeNegotiator
-    arguments: ['@access_check.theme']
-    parent: container.trait
+    arguments: ['@access_check.theme', '@class_resolver']
     tags:
       - { name: service_id_collector, tag: theme_negotiator }
   theme.negotiator.default:
diff -u b/core/lib/Drupal/Core/DependencyInjection/Compiler/TaggedHandlersPass.php b/core/lib/Drupal/Core/DependencyInjection/Compiler/TaggedHandlersPass.php
--- b/core/lib/Drupal/Core/DependencyInjection/Compiler/TaggedHandlersPass.php
+++ b/core/lib/Drupal/Core/DependencyInjection/Compiler/TaggedHandlersPass.php
@@ -23,9 +23,10 @@
  * second argument.
  *
  * To lazily instantiate services the service ID collector pattern can be used,
- * but the consumer service needs to be ContainerAware. As constructor injection
- * is used, processors cannot be added at runtime via this method. However, a
- * consuming service could have setter methods to allow runtime additions.
+ * but the consumer service needs to also inject the 'class_resolver' service.
+ * As constructor injection is used, processors cannot be added at runtime via
+ * this method. However, a consuming service could have setter methods to allow
+ * runtime additions.
  *
  * These differ from plugins in that all processors are explicitly registered by
  * service providers (driven by declarative configuration in code); the mere
@@ -87,14 +88,11 @@
    *   If at least one tagged service is required but none are found.
    */
   public function process(ContainerBuilder $container) {
-    foreach ($container->findTaggedServiceIds('service_collector') as $consumer_id => $passes) {
-      foreach ($passes as $pass) {
+    foreach ($container->getDefinitions() as $consumer_id => $definition) {
+      foreach ($definition->getTag('service_collector') as $pass) {
         $this->processServiceCollectorPass($pass, $consumer_id, $container);
       }
-    }
-
-    foreach ($container->findTaggedServiceIds('service_id_collector') as $consumer_id => $passes) {
-      foreach ($passes as $pass) {
+      foreach ($definition->getTag('service_id_collector') as $pass) {
         $this->processServiceIdCollectorPass($pass, $consumer_id, $container);
       }
     }
@@ -128,10 +126,10 @@
       if ($param->getClass()) {
         $interface = $param->getClass();
       }
-      else if ($param->getName() === 'id') {
+      elseif ($param->getName() === 'id') {
         $id_pos = $pos;
       }
-      else if ($param->getName() === 'priority') {
+      elseif ($param->getName() === 'priority') {
         $priority_pos = $pos;
       }
       else {
diff -u b/core/lib/Drupal/Core/Theme/ThemeNegotiator.php b/core/lib/Drupal/Core/Theme/ThemeNegotiator.php
--- b/core/lib/Drupal/Core/Theme/ThemeNegotiator.php
+++ b/core/lib/Drupal/Core/Theme/ThemeNegotiator.php
@@ -2,9 +2,8 @@
 
 namespace Drupal\Core\Theme;
 
+use Drupal\Core\DependencyInjection\ClassResolverInterface;
 use Drupal\Core\Routing\RouteMatchInterface;
-use Symfony\Component\DependencyInjection\ContainerAware;
-use Symfony\Component\DependencyInjection\ContainerAwareTrait;
 
 /**
  * Provides a class which determines the active theme of the page.
@@ -14,8 +13,6 @@
  */
 class ThemeNegotiator implements ThemeNegotiatorInterface {
 
-  use ContainerAwareTrait;
-
   /**
    * Holds an array of theme negotiator IDs, sorted by priority.
    *
@@ -31,16 +28,26 @@
   protected $themeAccess;
 
   /**
+   * The class resolver.
+   *
+   * @var \Drupal\Core\DependencyInjection\ClassResolverInterface
+   */
+  protected $classResolver;
+
+  /**
    * Constructs a new ThemeNegotiator.
    *
    * @param \Drupal\Core\Theme\ThemeAccessCheck $theme_access
    *   The access checker for themes.
+   * @param \Drupal\Core\DependencyInjection\ClassResolverInterface $class_resolver
+   *   The class resolver.
    * @param string[] $negotiators
    *   An array of negotiator IDs.
    */
-  public function __construct(ThemeAccessCheck $theme_access, array $negotiators) {
+  public function __construct(ThemeAccessCheck $theme_access, ClassResolverInterface $class_resolver, array $negotiators) {
     $this->themeAccess = $theme_access;
     $this->negotiators = $negotiators;
+    $this->classResolver = $class_resolver;
   }
 
   /**
@@ -55,7 +62,7 @@
    */
   public function determineActiveTheme(RouteMatchInterface $route_match) {
     foreach ($this->negotiators as $negotiator_id) {
-      $negotiator = $this->container->get($negotiator_id);
+      $negotiator = $this->classResolver->getInstanceFromDefinition($negotiator_id);
 
       if ($negotiator->applies($route_match)) {
         $theme = $negotiator->determineActiveTheme($route_match);
diff -u b/core/tests/Drupal/Tests/Core/Theme/ThemeNegotiatorTest.php b/core/tests/Drupal/Tests/Core/Theme/ThemeNegotiatorTest.php
--- b/core/tests/Drupal/Tests/Core/Theme/ThemeNegotiatorTest.php
+++ b/core/tests/Drupal/Tests/Core/Theme/ThemeNegotiatorTest.php
@@ -2,6 +2,7 @@
 
 namespace Drupal\Tests\Core\Theme;
 
+use Drupal\Core\DependencyInjection\ClassResolver;
 use Drupal\Core\DependencyInjection\ContainerBuilder;
 use Drupal\Core\Routing\RouteMatch;
 use Drupal\Core\Theme\ThemeNegotiator;
@@ -220,6 +221,8 @@
   protected function createThemeNegotiator(array $negotiators) {
-    $theme_negotiator = new ThemeNegotiator($this->themeAccessCheck, $negotiators);
-    $theme_negotiator->setContainer($this->container);
+    $resolver = new ClassResolver();
+    $resolver->setContainer($this->container);
+    $theme_negotiator = new ThemeNegotiator($this->themeAccessCheck, $resolver, $negotiators);
     return $theme_negotiator;
   }
+
 }