diff --git a/core/includes/install.core.inc b/core/includes/install.core.inc
index 1019270..2b1fca2 100644
--- a/core/includes/install.core.inc
+++ b/core/includes/install.core.inc
@@ -2182,6 +2182,16 @@ function install_write_profile($install_state) {
       'value' => $install_state['parameters']['profile'],
       'required' => TRUE,
     );
+  }
+  // Add specified base_profile to the settings profile_directories.
+  if (!empty($install_state['profile_info']['base_profile']) && isset($install_state['profiles'][$install_state['profile_info']['base_profile']]) && empty(Settings::get('profile_directories'))) {
+    $path = $install_state['profiles'][$install_state['profile_info']['base_profile']]->getPath();
+    $settings['settings']['profile_directories'] = (object) array(
+      'value' => array($path),
+      'required' => TRUE,
+    );
+  }
+  if (!empty($settings)) {
     drupal_rewrite_settings($settings);
   }
 }
diff --git a/core/lib/Drupal/Core/DrupalKernel.php b/core/lib/Drupal/Core/DrupalKernel.php
index 1c8068b..08826c3 100644
--- a/core/lib/Drupal/Core/DrupalKernel.php
+++ b/core/lib/Drupal/Core/DrupalKernel.php
@@ -744,6 +744,10 @@ protected function moduleData($module) {
       $profile_directories = array_map(function ($profile) {
         return $profile->getPath();
       }, $profiles);
+
+      // Allow additional profile directories to be added from settings.php.
+      // This provides support for "base profiles".
+      $profile_directories = array_merge(Settings::get('profile_directories', []), $profile_directories);
       $listing->setProfileDirectories($profile_directories);
 
       // Now find modules.
diff --git a/core/lib/Drupal/Core/Extension/ExtensionDiscovery.php b/core/lib/Drupal/Core/Extension/ExtensionDiscovery.php
index 337629b..83d0b6b 100644
--- a/core/lib/Drupal/Core/Extension/ExtensionDiscovery.php
+++ b/core/lib/Drupal/Core/Extension/ExtensionDiscovery.php
@@ -16,6 +16,13 @@
  * $settings['extension_discovery_scan_tests'] = TRUE;
  * @endcode
  * to your settings.php.
+ *
+ * To add additional profile directories, add
+ * @code
+ * $settings['profile_directories'] = array(path);
+ * @encode
+ * to your settings.php.  If multiple paths are specified, they are searched
+ * from last to first.
  */
 class ExtensionDiscovery {
 
@@ -250,6 +257,11 @@ public function setProfileDirectoriesFromSettings() {
     if ($profile) {
       $this->profileDirectories[] = drupal_get_path('profile', $profile);
     }
+
+    // Allow additional profile directories to be added from settings.php.
+    // This provides support for "base profiles".
+    $this->profileDirectories = array_merge(Settings::get('profile_directories', []), $this->profileDirectories);
+
     return $this;
   }
 
diff --git a/core/modules/system/tests/src/Kernel/System/ExtensionDiscoveryProfilesTest.php b/core/modules/system/tests/src/Kernel/System/ExtensionDiscoveryProfilesTest.php
new file mode 100644
index 0000000..9f0c03a
--- /dev/null
+++ b/core/modules/system/tests/src/Kernel/System/ExtensionDiscoveryProfilesTest.php
@@ -0,0 +1,69 @@
+<?php
+
+namespace Drupal\Tests\system\Kernel\System;
+
+use Drupal\Core\Extension\ExtensionDiscovery;
+use Drupal\Core\Site\Settings;
+use Drupal\KernelTests\KernelTestBase;
+use org\bovigo\vfs\vfsStream;
+use Symfony\Component\Yaml\Yaml;
+
+/**
+ * Tests setting profileDirectories from settings.
+ *
+ * @group Common
+ */
+class ExtensionDiscoveryProfilesTest extends KernelTestBase {
+  /**
+   * Tests that files in different directories take precedence as expected.
+   */
+  function testDirectoryPrecedence() {
+    // Set up the file system.
+    $filesystem = [];
+    $files_by_type_and_name_expected = $this->populateFilesystemStructure($filesystem);
+
+    $vfs = vfsStream::setup('root', NULL, $filesystem);
+    $root = $vfs->url();
+
+    // Define the module files we will search for, and the directory precedence
+    // we expect.
+    $expected_directories = array(
+      // When both copies of the module are compatible with Drupal core, the
+      // copy in the profile directory takes precedence.
+      'drupal_system_listing_compatible_test' => array(
+        'core/profiles/testing/modules',
+        'core/modules/system/tests/modules',
+      ),
+    );
+
+    // This test relies on two versions of the same module existing in
+    // different places in the filesystem. Without that, the test has no
+    // meaning, so assert their presence first.
+    foreach ($expected_directories as $module => $directories) {
+      foreach ($directories as $directory) {
+        $filename = "$directory/$module/$module.info.yml";
+        $this->assertFileExists($root . $filename);
+      }
+    }
+
+    // Now add the testing profile path to settings.
+    $settings = Settings::getAll();
+    $settings['profile_directories'] = array (
+      0 => 'core/profiles/testing',
+    );
+    new Settings($settings);
+
+    // Now scan the directories and check that the files take precedence as
+    // expected.
+    $listing = new ExtensionDiscovery($root);
+    $files = $listing->scan('module');
+    foreach ($expected_directories as $module => $directories) {
+      $expected_directory = array_shift($directories);
+      $expected_uri = "$expected_directory/$module/$module.info.yml";
+      $this->assertEqual($files[$module]->getPathname(), $expected_uri, format_string('Module @actual was found at @expected.', array(
+        '@actual' => $files[$module]->getPathname(),
+        '@expected' => $expected_uri,
+      )));
+    }
+  }
+}