@@ -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
@@ -49,20 +49,20 @@
  * @brief Returns the next list item of the list item.
  *
  * @param listItem The list item for which the next list item should be returned
  * @return The next list item of the list item
  */
-OFListItem OFListItemNext(OFListItem _Nonnull listItem);
+extern OFListItem _Nullable OFListItemNext(OFListItem _Nonnull listItem);
 
 /*!
  * @brief Returns the previous list item of the list item.
  *
  * @param listItem The list item for which the previous list item should be
  *		   returned
  * @return The previous list item of the list item
  */
-OFListItem OFListItemPrevious(OFListItem _Nonnull listItem);
+extern OFListItem _Nullable OFListItemPrevious(OFListItem _Nonnull listItem);
 
 /*!
  * @brief Returns the object of the list item.
  *
  * @warning The returned object is not retained and autoreleased - this is the
@@ -69,11 +69,11 @@
  *	    caller's responsibility!
  *
  * @param listItem The list item for which the object should be returned
  * @return The object of the list item
  */
-id OFListItemObject(OFListItem _Nonnull listItem);
+extern id _Nonnull OFListItemObject(OFListItem _Nonnull listItem);
 #ifdef __cplusplus
 }
 #endif
 
 /**