diff --git a/core/Migrations/Version21000Date20210309185127.php b/core/Migrations/Version21000Date20210309185127.php
new file mode 100644
index 0000000000000000000000000000000000000000..01cbdcb8641bb7e818da1acb901692f8128fe9e2
--- /dev/null
+++ b/core/Migrations/Version21000Date20210309185127.php
@@ -0,0 +1,52 @@
+<?php
+
+declare(strict_types=1);
+/**
+ * @copyright Copyright (c) 2021 Joas Schilling <coding@schilljs.com>
+ *
+ * @author Joas Schilling <coding@schilljs.com>
+ *
+ * @license GNU AGPL version 3 or any later version
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU Affero General Public License as
+ * published by the Free Software Foundation, either version 3 of the
+ * License, or (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU Affero General Public License for more details.
+ *
+ * You should have received a copy of the GNU Affero General Public License
+ * along with this program. If not, see <http://www.gnu.org/licenses/>.
+ */
+
+
+namespace OC\Core\Migrations;
+
+use Closure;
+use OCP\DB\ISchemaWrapper;
+use OCP\Migration\IOutput;
+use OCP\Migration\SimpleMigrationStep;
+
+class Version21000Date20210309185127 extends SimpleMigrationStep {
+	/**
+	 * @param IOutput $output
+	 * @param Closure $schemaClosure The `\Closure` returns a `ISchemaWrapper`
+	 * @param array $options
+	 * @return null|ISchemaWrapper
+	 */
+	public function changeSchema(IOutput $output, Closure $schemaClosure, array $options): ?ISchemaWrapper {
+		/** @var ISchemaWrapper $schema */
+		$schema = $schemaClosure();
+
+		$table = $schema->getTable('known_users');
+		if (!$table->hasIndex('ku_known_user')) {
+			$table->addIndex(['known_user'], 'ku_known_user');
+			return $schema;
+		}
+
+		return null;
+	}
+}
diff --git a/lib/composer/composer/autoload_classmap.php b/lib/composer/composer/autoload_classmap.php
index fd3dc44f26c2f358389de8e13705d900bf4e1cf1..a150fca9528e0f362ddb7aab7593622b926d1a7e 100644
--- a/lib/composer/composer/autoload_classmap.php
+++ b/lib/composer/composer/autoload_classmap.php
@@ -953,6 +953,7 @@ return array(
     'OC\\Core\\Migrations\\Version21000Date20201202095923' => $baseDir . '/core/Migrations/Version21000Date20201202095923.php',
     'OC\\Core\\Migrations\\Version21000Date20210119195004' => $baseDir . '/core/Migrations/Version21000Date20210119195004.php',
     'OC\\Core\\Migrations\\Version21000Date20210309185126' => $baseDir . '/core/Migrations/Version21000Date20210309185126.php',
+    'OC\\Core\\Migrations\\Version21000Date20210309185127' => $baseDir . '/core/Migrations/Version21000Date20210309185127.php',
     'OC\\Core\\Notification\\CoreNotifier' => $baseDir . '/core/Notification/CoreNotifier.php',
     'OC\\Core\\Service\\LoginFlowV2Service' => $baseDir . '/core/Service/LoginFlowV2Service.php',
     'OC\\DB\\Adapter' => $baseDir . '/lib/private/DB/Adapter.php',
diff --git a/lib/composer/composer/autoload_static.php b/lib/composer/composer/autoload_static.php
index 797c4b325def3fff149e7fb698b47c291d34fa26..5cb5efbd5d350604ac8aa72fea8c006517d4c518 100644
--- a/lib/composer/composer/autoload_static.php
+++ b/lib/composer/composer/autoload_static.php
@@ -982,6 +982,7 @@ class ComposerStaticInit53792487c5a8370acc0b06b1a864ff4c
         'OC\\Core\\Migrations\\Version21000Date20201202095923' => __DIR__ . '/../../..' . '/core/Migrations/Version21000Date20201202095923.php',
         'OC\\Core\\Migrations\\Version21000Date20210119195004' => __DIR__ . '/../../..' . '/core/Migrations/Version21000Date20210119195004.php',
         'OC\\Core\\Migrations\\Version21000Date20210309185126' => __DIR__ . '/../../..' . '/core/Migrations/Version21000Date20210309185126.php',
+        'OC\\Core\\Migrations\\Version21000Date20210309185127' => __DIR__ . '/../../..' . '/core/Migrations/Version21000Date20210309185127.php',
         'OC\\Core\\Notification\\CoreNotifier' => __DIR__ . '/../../..' . '/core/Notification/CoreNotifier.php',
         'OC\\Core\\Service\\LoginFlowV2Service' => __DIR__ . '/../../..' . '/core/Service/LoginFlowV2Service.php',
         'OC\\DB\\Adapter' => __DIR__ . '/../../..' . '/lib/private/DB/Adapter.php',