diff --git a/lib/public/Lock/ManuallyLockedException.php b/lib/public/Lock/ManuallyLockedException.php
index 71d9a7282abd7449d5436a8f1c01c5d326fc0a67..04b4152c3a0774124c64321abe0e0054739a77eb 100644
--- a/lib/public/Lock/ManuallyLockedException.php
+++ b/lib/public/Lock/ManuallyLockedException.php
@@ -65,7 +65,7 @@ class ManuallyLockedException extends LockedException {
 	 *
 	 * @since 18.0.0
 	 */
-	public function __construct(string $path, \Exception $previous = null, string $existingLock = null, string $owner = null, int $timeout = -1) {
+	public function __construct(string $path, \Exception $previous = null, ?string $existingLock = null, ?string $owner = null, int $timeout = -1) {
 		parent::__construct($path, $previous, $existingLock);
 		$this->owner = $owner;
 		$this->timeout = $timeout;