diff --git a/lib/private/Preview/BackgroundCleanupJob.php b/lib/private/Preview/BackgroundCleanupJob.php
index 6d83741e7e3b9..28dca276026e0 100644
--- a/lib/private/Preview/BackgroundCleanupJob.php
+++ b/lib/private/Preview/BackgroundCleanupJob.php
@@ -36,6 +36,9 @@
 
 class BackgroundCleanupJob extends TimedJob {
 
+	/** @var IConfig */
+	private $config;
+
 	/** @var IDBConnection */
 	private $connection;
 
diff --git a/tests/lib/Preview/BackgroundCleanupJobTest.php b/tests/lib/Preview/BackgroundCleanupJobTest.php
index 5ac7593ae568e..80aafa9aa4281 100644
--- a/tests/lib/Preview/BackgroundCleanupJobTest.php
+++ b/tests/lib/Preview/BackgroundCleanupJobTest.php
@@ -50,6 +50,9 @@ class BackgroundCleanupJobTest extends \Test\TestCase {
 	/** @var bool */
 	private $trashEnabled;
 
+	/** @var IConfig */
+	private $config;
+
 	/** @var IDBConnection */
 	private $connection;