diff -u b/core/lib/Drupal/Core/Config/ConfigInstaller.php b/core/lib/Drupal/Core/Config/ConfigInstaller.php
--- b/core/lib/Drupal/Core/Config/ConfigInstaller.php
+++ b/core/lib/Drupal/Core/Config/ConfigInstaller.php
@@ -10,6 +10,7 @@
 use Drupal\Component\Utility\Unicode;
 use Drupal\Core\Config\Entity\ConfigDependencyManager;
 use Drupal\Core\Entity\EntityTypeInterface;
+use Drupal\Core\Site\Settings;
 use Symfony\Component\EventDispatcher\EventDispatcherInterface;
 
 class ConfigInstaller implements ConfigInstallerInterface {
@@ -161,13 +162,19 @@
    */
   public function installOptionalConfig(StorageInterface $storage = NULL, $prefix = '') {
     if (!$storage) {
-      // Optional configuration in the profile can never be used.
-      $storage = new ExtensionInstallStorage($this->getActiveStorages(StorageInterface::DEFAULT_COLLECTION), InstallStorage::CONFIG_OPTIONAL_DIRECTORY, StorageInterface::DEFAULT_COLLECTION, FALSE);
+      // Search the install profile's optional configuration too.
+      $storage = new ExtensionInstallStorage($this->getActiveStorages(StorageInterface::DEFAULT_COLLECTION), InstallStorage::CONFIG_OPTIONAL_DIRECTORY, StorageInterface::DEFAULT_COLLECTION, TRUE);
+      // The extension install storage ensures that overrides are used.
+      $profile_storage = NULL;
+    }
+    else {
+      // Creates a profile storage to search for overrides.
+      $profile_install_path = $this->drupalGetPath('module', $this->drupalGetProfile()) . '/' . InstallStorage::CONFIG_OPTIONAL_DIRECTORY;
+      $profile_storage = new FileStorage($profile_install_path, StorageInterface::DEFAULT_COLLECTION);
     }
+
     $collection_info = $this->configManager->getConfigCollectionInfo();
     $enabled_extensions = $this->getEnabledExtensions();
-    // Gets a profile storage to search for overrides if necessary.
-    $profile_storage = $this->getProfileStorage();
 
     foreach ($collection_info->getCollectionNames() as $collection) {
       if (!$this->configManager->supportsConfigurationEntities($collection)) {
@@ -593,7 +600,7 @@
   }
 
   /**
-   * Wrapper for drupal_get_profile().
+   * Gets the install profile from settings.
    *
    * @return string|null $profile
    *   The name of the installation profile or NULL if no installation profile
@@ -601,7 +608,9 @@
    *   of the installer or during unit tests.
    */
   protected function drupalGetProfile() {
-    return drupal_get_profile();
+    // Settings is safe to use because settings.php is written before any module
+    // is installed.
+    return Settings::get('install_profile');
   }
 
   /**
diff -u b/core/modules/config/src/Tests/ConfigInstallProfileOverrideTest.php b/core/modules/config/src/Tests/ConfigInstallProfileOverrideTest.php
--- b/core/modules/config/src/Tests/ConfigInstallProfileOverrideTest.php
+++ b/core/modules/config/src/Tests/ConfigInstallProfileOverrideTest.php
@@ -78,13 +78,43 @@
     $tour = Tour::load('language-add');
     $this->assertEqual(count($tour->getTips()), 3, 'Optional configuration that is not overridden is not affected.');
 
-    // Ensure that optional configuration is not installed from a profile.
-    $id = 'testing_config_overrides';
-    $this->assertNull(Tour::load($id), 'The tour contained in the profile\'s optional directory does not exist.');
-    // Make that we don't get false positives from the assertion above.
+    // Ensure that optional configuration from a profile is created if
+    // dependencies are met.
+    $this->assertEqual(Tour::load('testing_config_overrides')->label(), 'Config override test');
+
+    // Ensure that optional configuration from a profile is not created if
+    // dependencies are not met. Cannot use the entity system since the entity
+    // type does not exist.
     $optional_dir = drupal_get_path('module', 'testing_config_overrides') . '/' . InstallStorage::CONFIG_OPTIONAL_DIRECTORY;
-    $storage = new FileStorage($optional_dir);
-    $this->assertTrue($storage->exists('tour.tour.' . $id), 'The tour does exist in the profile\'s optional directory.');
+    $optional_storage = new FileStorage($optional_dir);
+    foreach (['config_test.dynamic.dotted.default', 'config_test.dynamic.override','config_test.dynamic.override_unmet'] as $id) {
+      $this->assertTrue(\Drupal::config($id)->isNew(), "The config_test entity $id contained in the profile's optional directory does not exist.");
+      // Make that we don't get false positives from the assertion above.
+      $this->assertTrue($optional_storage->exists($id), "The config_test entity $id does exist in the profile's optional directory.");
+    }
+
+    // Install the config_test module and ensure that the override from the
+    // install profile is not used. Optional configuration can not override
+    // configuration in a modules config/install directory.
+    $this->container->get('module_installer')->install(['config_test']);
+    $this->rebuildContainer();
+    $config_test_storage = \Drupal::entityManager()->getStorage('config_test');
+    $this->assertEqual($config_test_storage->load('dotted.default')->label(), 'Default', 'The config_test entity is not overridden by the profile optional configuration.');
+    // Test that override of optional configuration does work.
+    $this->assertEqual($config_test_storage->load('override')->label(), 'Override', 'The optional config_test entity is overridden by the profile optional configuration.');
+    // Test that override of optional configuration which introduces an unmet
+    // dependency does not get created.
+    $this->assertNull($config_test_storage->load('override_unmet'), 'The optional config_test entity with unmet dependencies is not created.');
+
+    $this->container->get('module_installer')->install(['dblog']);
+    $this->rebuildContainer();
+    // Just installing db_log does not create the optional configuration.
+    $this->assertNull($config_test_storage->load('override_unmet'), 'The optional config_test entity with unmet dependencies is not created.');
+    // Install all available optional configuration.
+    $this->container->get('config.installer')->installOptionalConfig();
+    $this->assertEqual($config_test_storage->load('override_unmet')->label(), 'Override', 'The optional config_test entity is overridden by the profile optional configuration.');
+
+
   }
 
 }
only in patch2:
unchanged:
--- a/core/lib/Drupal/Core/Config/ExtensionInstallStorage.php
+++ b/core/lib/Drupal/Core/Config/ExtensionInstallStorage.php
@@ -45,7 +45,7 @@ class ExtensionInstallStorage extends InstallStorage {
    *   default collection.
    * @param bool $include_profile
    *   (optional) Whether to include the install profile in extensions to
-   *   search.
+   *   search and to get overrides from.
    */
   public function __construct(StorageInterface $config_storage, $directory = self::CONFIG_INSTALL_DIRECTORY, $collection = StorageInterface::DEFAULT_COLLECTION, $include_profile = TRUE) {
     $this->configStorage = $config_storage;
@@ -82,27 +82,24 @@ protected function getAllFolders() {
       $this->folders = array();
       $this->folders += $this->getComponentNames('core', array('core'));
 
+      $install_profile = Settings::get('install_profile');
       $extensions = $this->configStorage->read('core.extension');
       if (!empty($extensions['module'])) {
         $modules = $extensions['module'];
-        if (!$this->includeProfile) {
-          if ($install_profile = Settings::get('install_profile')) {
-            unset($modules[$install_profile]);
-          }
-        }
+        // Remove the install profile as this is handled later.
+        unset($modules[$install_profile]);
         $this->folders += $this->getComponentNames('module', array_keys($modules));
       }
       if (!empty($extensions['theme'])) {
         $this->folders += $this->getComponentNames('theme', array_keys($extensions['theme']));
       }
 
-      // The install profile can override module default configuration. We do
-      // this by replacing the config file path from the module/theme with the
-      // install profile version if there are any duplicates.
-      $profile_folders = $this->getComponentNames('profile', array(drupal_get_profile()));
-      $folders_to_replace = array_intersect_key($profile_folders, $this->folders);
-      if (!empty($folders_to_replace)) {
-        $this->folders = array_merge($this->folders, $folders_to_replace);
+      if ($this->includeProfile) {
+        // The install profile can override module default configuration. We do
+        // this by replacing the config file path from the module/theme with the
+        // install profile version if there are any duplicates.
+        $profile_folders = $this->getComponentNames('profile', array(drupal_get_profile()));
+        $this->folders = $profile_folders + $this->folders;
       }
     }
     return $this->folders;
only in patch2:
unchanged:
--- /dev/null
+++ b/core/modules/config/tests/config_test/config/optional/config_test.dynamic.override.yml
@@ -0,0 +1,6 @@
+# See \Drupal\config\Tests\ConfigInstallProfileOverrideTest
+id: override
+label: Default
+weight: 0
+protected_property: Default
+status: 1
only in patch2:
unchanged:
--- /dev/null
+++ b/core/modules/config/tests/config_test/config/optional/config_test.dynamic.override_unmet.yml
@@ -0,0 +1,10 @@
+# See \Drupal\config\Tests\ConfigInstallProfileOverrideTest
+# This configuration entity has dependencies which would be met.
+id: override_unmet
+label: Default
+weight: 0
+protected_property: Default
+status: 1
+dependencies:
+  module:
+    - tour
\ No newline at end of file
only in patch2:
unchanged:
--- /dev/null
+++ b/core/profiles/testing_config_overrides/config/optional/config_test.dynamic.dotted.default.yml
@@ -0,0 +1,6 @@
+id: dotted.default
+label: 'Default install profile override'
+weight: 0
+protected_property: Default
+# Intentionally commented out to verify default status behavior.
+# status: 1
only in patch2:
unchanged:
--- /dev/null
+++ b/core/profiles/testing_config_overrides/config/optional/config_test.dynamic.override.yml
@@ -0,0 +1,8 @@
+id: override
+label: Override
+weight: 0
+protected_property: Default
+status: 1
+dependencies:
+  module:
+    - tour
\ No newline at end of file
only in patch2:
unchanged:
--- /dev/null
+++ b/core/profiles/testing_config_overrides/config/optional/config_test.dynamic.override_unmet.yml
@@ -0,0 +1,8 @@
+id: override_unmet
+label: Override
+weight: 0
+protected_property: Default
+status: 1
+dependencies:
+  module:
+    - dblog
\ No newline at end of file