diff --git a/core/lib/Drupal/Core/Config/ConfigInstaller.php b/core/lib/Drupal/Core/Config/ConfigInstaller.php
index 8906eba..b8b0262 100644
--- a/core/lib/Drupal/Core/Config/ConfigInstaller.php
+++ b/core/lib/Drupal/Core/Config/ConfigInstaller.php
@@ -212,6 +212,33 @@ public function installOptionalConfig(StorageInterface $storage = NULL, $depende
   }
 
   /**
+   * {@inheritdoc}
+   */
+  public function installNewConfig($type, $name, array $config_names) {
+
+    $config_not_found = $config_names;
+    foreach ([InstallStorage::CONFIG_INSTALL_DIRECTORY, InstallStorage::CONFIG_OPTIONAL_DIRECTORY] as $location) {
+      $config_path = $this->drupalGetPath($type, $name) . '/' . $location;
+      $storage = new NewConfigStorage($config_path, StorageInterface::DEFAULT_COLLECTION, $config_names);
+
+      // Check for existing configuration.
+      $existing = $this->findPreExistingConfiguration($storage);
+      if (!empty($existing)) {
+        throw PreExistingConfigException::create($name, $existing);
+      }
+
+      $config_not_found = array_diff($config_names, $storage->listAll());
+
+      // Install the new configuration.
+      $this->installOptionalConfig($storage);
+    }
+
+    if (!empty($config_not_found)) {
+      throw new ConfigNameException('Could not find the following configurations: ' . implode(', ', $config_not_found));
+    }
+  }
+
+  /**
    * Gets configuration data from the provided storage to create.
    *
    * @param StorageInterface $storage
diff --git a/core/lib/Drupal/Core/Config/ConfigInstallerInterface.php b/core/lib/Drupal/Core/Config/ConfigInstallerInterface.php
index ac7ca09..df68c62 100644
--- a/core/lib/Drupal/Core/Config/ConfigInstallerInterface.php
+++ b/core/lib/Drupal/Core/Config/ConfigInstallerInterface.php
@@ -58,6 +58,23 @@ public function installDefaultConfig($type, $name);
   public function installOptionalConfig(StorageInterface $storage = NULL, $dependency = []);
 
   /**
+   * Installs new configuration for a given extension.
+   *
+   * This is only intended to be used with configuration that is added after a
+   * module has already been installed.
+   *
+   * @param string $type
+   *   The extension type; e.g., 'module' or 'theme'.
+   * @param string $name
+   *   The name of the module or theme to install default configuration for.
+   * @param array $config_names
+   *   An array of configuration names to import.
+   *
+   * @throws \Drupal\Core\Config\PreExistingConfigException
+   */
+  public function installNewConfig($type, $name, array $config_names);
+
+  /**
    * Installs all default configuration in the specified collection.
    *
    * The function is useful if the site needs to respond to an event that has
diff --git a/core/lib/Drupal/Core/Config/NewConfigStorage.php b/core/lib/Drupal/Core/Config/NewConfigStorage.php
new file mode 100644
index 0000000..d2450e9
--- /dev/null
+++ b/core/lib/Drupal/Core/Config/NewConfigStorage.php
@@ -0,0 +1,60 @@
+<?php
+
+/**
+ * @file
+ * Contains \Drupal\Core\Config\NewConfigStorage.
+ */
+
+namespace Drupal\Core\Config;
+
+use Drupal\Core\Site\Settings;
+use Drupal\Core\Extension\ExtensionDiscovery;
+
+/**
+ * Storage for new configuration that is added after extension installation.
+ *
+ * @see \Drupal\Core\Config\ConfigInstaller
+ * @see \Drupal\Core\Config\TypedConfigManager
+ */
+class NewConfigStorage extends FileStorage {
+
+  /**
+   * List of configuration names to include.
+   *
+   * @var array
+   */
+  protected $configNames = [];
+
+  /**
+   * {@inheritdoc}
+   *
+   * @param array $config_names
+   *   List of config names to include.
+   */
+  public function __construct($directory, $collection = StorageInterface::DEFAULT_COLLECTION, array $config_names) {
+    parent::__construct($directory, $collection);
+    $this->configNames = $config_names;
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function createCollection($collection) {
+    return new static(
+      $this->directory,
+      $collection,
+      $this->configNames
+    );
+  }
+
+  /**
+   * {@inheritdoc}
+   *
+   * Additionally filter by self::$configNames().
+   */
+  public function listAll($prefix = '') {
+    return array_intersect($this->configNames, parent::listAll($prefix));
+  }
+
+}
+
diff --git a/core/lib/Drupal/Core/ProxyClass/Config/ConfigInstaller.php b/core/lib/Drupal/Core/ProxyClass/Config/ConfigInstaller.php
index 3eff9a8..f520385 100644
--- a/core/lib/Drupal/Core/ProxyClass/Config/ConfigInstaller.php
+++ b/core/lib/Drupal/Core/ProxyClass/Config/ConfigInstaller.php
@@ -2,7 +2,7 @@
 
 /**
  * @file
- * Contains Drupal\Core\ProxyClass\Config\ConfigInstaller.
+ * Contains \Drupal\Core\ProxyClass\Config\ConfigInstaller.
  */
 
 /**
@@ -91,6 +91,14 @@ public function installOptionalConfig(\Drupal\Core\Config\StorageInterface $stor
         /**
          * {@inheritdoc}
          */
+        public function installNewConfig($type, $name, array $config_names)
+        {
+            return $this->lazyLoadItself()->installNewConfig($type, $name, $config_names);
+        }
+
+        /**
+         * {@inheritdoc}
+         */
         public function installCollectionDefaultConfig($collection)
         {
             return $this->lazyLoadItself()->installCollectionDefaultConfig($collection);