diff --git a/core/modules/system/src/Tests/Update/StableBaseThemeUpdateTest.php b/core/modules/system/src/Tests/Update/StableBaseThemeUpdateTest.php
new file mode 100644
index 0000000..565fa0d
--- /dev/null
+++ b/core/modules/system/src/Tests/Update/StableBaseThemeUpdateTest.php
@@ -0,0 +1,53 @@
+<?php
+
+/**
+ * @file
+ * Contains \Drupal\system\Tests\Update\StableBaseThemeUpdateTest.
+ */
+
+namespace Drupal\system\Tests\Update;
+
+/**
+ * Tests the upgrade path for the Stable base theme.
+ *
+ * @see https://www.drupal.org/node/2575421
+ *
+ * @group system
+ */
+class StableBaseThemeUpdateTest extends UpdatePathTestBase {
+
+  /**
+   * {@inheritdoc}
+   */
+  protected function setDatabaseDumpFiles() {
+    $this->databaseDumpFiles = [
+      __DIR__ . '/../../../../system/tests/fixtures/update/drupal-8.bare.standard.php.gz',
+      __DIR__ . '/../../../../system/tests/fixtures/update/drupal-8.stable-base-theme-2575421.php',
+    ];
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  protected function setUp() {
+    parent::setUp();
+    /** @var \Drupal\Core\Extension\ThemeHandlerInterface $theme_handler */
+    $theme_handler = \Drupal::service('theme_handler');
+    $theme_handler->refreshInfo();
+  }
+
+  /**
+   * Tests that the Stable base theme is installed if necessary.
+   */
+  public function testUpdateHookN() {
+    $theme_handler = \Drupal::service('theme_handler');
+    $this->assertTrue($theme_handler->themeExists('test_stable'));
+    $this->assertFalse($theme_handler->themeExists('stable'));
+
+    $this->runUpdates();
+
+    $theme_handler->refreshInfo();
+    $this->assertTrue($theme_handler->themeExists('stable'));
+  }
+
+}
diff --git a/core/modules/system/tests/fixtures/update/drupal-8.stable-base-theme-2575421.php b/core/modules/system/tests/fixtures/update/drupal-8.stable-base-theme-2575421.php
new file mode 100644
index 0000000..7b658b4
--- /dev/null
+++ b/core/modules/system/tests/fixtures/update/drupal-8.stable-base-theme-2575421.php
@@ -0,0 +1,25 @@
+<?php
+
+/**
+ * @file
+ * Contains database additions to drupal-8.bare.standard.php.gz for testing the
+ * upgrade path of https://www.drupal.org/node/2575421.
+ */
+
+use Drupal\Core\Database\Database;
+
+$connection = Database::getConnection();
+
+// Enable test_stable theme.
+$extensions = $connection->select('config')
+  ->fields('config', ['data'])
+  ->condition('name', 'core.extension')
+  ->execute()
+  ->fetchField();
+$extensions = unserialize($extensions);
+$connection->update('config')
+  ->fields([
+    'data' => serialize(array_merge_recursive($extensions, ['theme' => ['test_stable' => 0]]))
+  ])
+  ->condition('name', 'core.extension')
+  ->execute();