@@ -1,7 +1,7 @@
 /*
- * Copyright (c) 2008-2021 Jonathan Schleifer <js@nil.im>
+ * Copyright (c) 2008-2022 Jonathan Schleifer <js@nil.im>
  *
  * All rights reserved.
  *
  * This file is part of ObjFW. It may be distributed under the terms of the
  * Q Public License 1.0, which can be found in the file LICENSE.QPL included in
@@ -24,11 +24,11 @@
  *
  * @brief An exception indicating that a lock is still locked.
  */
 @interface OFStillLockedException: OFException
 {
-	id <OFLocking> _lock;
+	id <OFLocking> _Nullable _lock;
 }
 
 /**
  * @brief The lock which is still locked.
  */