diff --git a/core/modules/system/src/Tests/Entity/Update/SqlContentEntityStorageSchemaIndexTest.php b/core/modules/system/src/Tests/Entity/Update/SqlContentEntityStorageSchemaIndexTest.php
new file mode 100644
index 0000000..a7078ba
--- /dev/null
+++ b/core/modules/system/src/Tests/Entity/Update/SqlContentEntityStorageSchemaIndexTest.php
@@ -0,0 +1,40 @@
+<?php
+
+/**
+ * @file
+ * Contains \Drupal\system\Tests\Entity\Update\SqlContentEntityStorageSchemaIndexTest.
+ */
+
+namespace Drupal\system\Tests\Entity\Update;
+
+use Drupal\system\Tests\Update\UpdatePathTestBase;
+
+/**
+ * Tests that a newly-added index is properly created during database updates.
+ *
+ * @group Entity
+ */
+class SqlContentEntityStorageSchemaIndexTest extends UpdatePathTestBase {
+
+  /**
+   * {@inheritdoc}
+   */
+  public function setUp() {
+    $this->databaseDumpFiles = [
+      __DIR__ . '/../../../../tests/fixtures/update/drupal-8.bare.standard.php.gz',
+    ];
+    parent::setUp();
+  }
+
+  /**
+   * Test for the new index.
+   */
+  public function testIndex() {
+    $this->assertFalse(db_index_exists('node_field_data', 'node__id__default_langcode__langcode'), 'Index node__id__default_langcode__langcode does not exist prior to running updates.');
+    $this->assertFalse(db_index_exists('users_field_data', 'user__id__default_langcode__langcode'), 'Index users__id__default_langcode__langcode does not exist prior to running updates.');
+    $this->runUpdates();
+    $this->assertTrue(db_index_exists('node_field_data', 'node__id__default_langcode__langcode'), 'Index node__id__default_langcode__langcode properly created on the node_field_data table.');
+    $this->assertTrue(db_index_exists('users_field_data', 'user__id__default_langcode__langcode'), 'Index users__id__default_langcode__langcode properly created on the user_field_data table.');
+  }
+
+}