diff --git a/core/Migrations/Version15000Date20180927120000.php b/core/Migrations/Version15000Date20180927120000.php
index d5c4b3364f..5636811baa 100644
--- a/core/Migrations/Version15000Date20180927120000.php
+++ b/core/Migrations/Version15000Date20180927120000.php
@@ -38,9 +38,9 @@ class Version15000Date20180927120000 extends SimpleMigrationStep {
 
 		$table = $schema->getTable('cards');
 		$table->addColumn('uid', Type::STRING, [
-			'notnull' => true,
-			'length' => 255]
-		);
+			'notnull' => false,
+			'length' => 255
+		]);
 
 		return $schema;
 	}
diff --git a/lib/private/Repair/NC15/SetVcardDatabaseUID.php b/lib/private/Repair/NC15/SetVcardDatabaseUID.php
new file mode 100644
index 0000000000..2fe50c7947
--- /dev/null
+++ b/lib/private/Repair/NC15/SetVcardDatabaseUID.php
@@ -0,0 +1,127 @@
+<?php
+/**
+ * @copyright Copyright (c) 2018 John Molakvoæ <skjnldsv@protonmail.com>
+ *
+ * @author John Molakvoæ <skjnldsv@protonmail.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\Repair\NC13;
+
+
+use OCP\DB\QueryBuilder\IQueryBuilder;
+use OCP\IConfig;
+use OCP\IDBConnection;
+use OCP\Migration\IOutput;
+use OCP\Migration\IRepairStep;
+
+class SetVcardDatabaseUID implements IRepairStep {
+	const MAX_ROWS = 1000;
+
+	/** @var IDBConnection */
+	private $connection;
+	private $updateQuery;
+
+	public function __construct(IDBConnection $connection) {
+		$this->connection = $connection;
+	}
+
+
+	public function getName() {
+		return 'Extract the vcard uid and store it in the db';
+	}
+
+	/**
+	 * @return \Generator
+	 * @suppress SqlInjectionChecker
+	 */
+	private function getInvalidEntries() {
+		$builder = $this->connection->getQueryBuilder();
+
+		$builder->select('id', 'carddata')
+			->from('cards')
+			->where($builder->expr()->isNull('uid'))
+			->setMaxResults(self::MAX_ROWS);
+
+		do {
+			$result = $builder->execute();
+			$rows = $result->fetchAll();
+			foreach ($rows as $row) {
+				yield $row;
+			}
+			$result->closeCursor();
+		} while (count($rows) > 0);
+	}
+
+	private function getUid($carddata) {
+		preg_match('/^UID:(.*)$/m', $carddata, $matches);
+		if (count($matches > 1)) {
+			return $matches[1][0];
+		}
+		return false;
+	}
+
+	/**
+	 * @param int $id
+	 * @param string $uid
+	 */
+	private function update($id, $uid) {
+		if (!$this->updateQuery) {
+			$builder = $this->connection->getQueryBuilder();
+
+			$this->updateQuery = $builder->update('cards')
+				->set('uid', $builder->createParameter('uid'))
+				->where($builder->expr()->eq('id', $builder->createParameter('id')));
+		}
+
+		$this->updateQuery->setParameter('id', $id);
+		$this->updateQuery->setParameter('uid', $uid);
+
+		$this->updateQuery->execute();
+	}
+
+	private function repair() {
+		$this->connection->beginTransaction();
+		$entries = $this->getInvalidEntries();
+		$count = 0;
+		foreach ($entries as $entry) {
+			$count++;
+			$uid = $this->getUid($entry['id']);
+			if ($uid !== false) {
+				$this->update($entry['id'], $uid);
+			}
+		}
+		$this->connection->commit();
+		return $count;
+	}
+
+	private function shouldRun() {
+		$versionFromBeforeUpdate = $this->config->getSystemValue('version', '0.0.0');
+
+		// was added to 15.0.0.0
+		return version_compare($versionFromBeforeUpdate, '15.0.0.0', '<=');
+	}
+
+	public function run(IOutput $output) {
+		if ($this->shouldRun()) {
+			$count = $this->repair();
+
+			$output->info('Fixed ' . $count . ' vcards');
+		}
+	}
+}