diff --git a/core/lib/Drupal/Core/DependencyInjection/Compiler/ModifyServiceDefinitionsPass.php b/core/lib/Drupal/Core/DependencyInjection/Compiler/ModifyServiceDefinitionsPass.php
index 25614e3..8ecded9 100644
--- a/core/lib/Drupal/Core/DependencyInjection/Compiler/ModifyServiceDefinitionsPass.php
+++ b/core/lib/Drupal/Core/DependencyInjection/Compiler/ModifyServiceDefinitionsPass.php
@@ -28,7 +28,13 @@ public function process(ContainerBuilder $container) {
     if (!($kernel instanceof DrupalKernelInterface)) {
       return;
     }
-    $providers = $kernel->getServiceProviders();
+    $providers = $kernel->getServiceProviders('app');
+    foreach ($providers as $provider) {
+      if ($provider instanceof ServiceModifierInterface) {
+        $provider->alter($container);
+      }
+    }
+    $providers = $kernel->getServiceProviders('site');
     foreach ($providers as $provider) {
       if ($provider instanceof ServiceModifierInterface) {
         $provider->alter($container);
diff --git a/core/lib/Drupal/Core/DrupalKernel.php b/core/lib/Drupal/Core/DrupalKernel.php
index 35341ce..f286615 100644
--- a/core/lib/Drupal/Core/DrupalKernel.php
+++ b/core/lib/Drupal/Core/DrupalKernel.php
@@ -259,7 +259,7 @@ public function discoverServiceProviders() {
     if (!empty($GLOBALS['conf']['container_yamls'])) {
       $this->serviceYamls['site'] = $GLOBALS['conf']['container_yamls'];
     }
-    if ($exists = file_exists($site_services_yml = conf_path() . '/services.yml')) {
+    if (file_exists($site_services_yml = conf_path() . '/services.yml')) {
       $this->serviceYamls['site'][] = $site_services_yml;
     }
   }
@@ -267,8 +267,8 @@ public function discoverServiceProviders() {
   /**
    * {@inheritdoc}
    */
-  public function getServiceProviders() {
-    return $this->serviceProviders;
+  public function getServiceProviders($origin) {
+    return $this->serviceProviders[$origin];
   }
 
   /**
diff --git a/core/lib/Drupal/Core/DrupalKernelInterface.php b/core/lib/Drupal/Core/DrupalKernelInterface.php
index 544b44c..1e2ed07 100644
--- a/core/lib/Drupal/Core/DrupalKernelInterface.php
+++ b/core/lib/Drupal/Core/DrupalKernelInterface.php
@@ -38,10 +38,13 @@ public function discoverServiceProviders();
   /**
    * Returns all registered service providers.
    *
+   * @param string $origin
+   *   The origin for which to return service providers; one of 'app' or 'site'.
+   *
    * @return array
    *   An associative array of ServiceProvider objects, keyed by name.
    */
-  public function getServiceProviders();
+  public function getServiceProviders($origin);
 
   /**
    * Gets the current container.