Index: Doxyfile
==================================================================
--- Doxyfile
+++ Doxyfile
@@ -4,25 +4,26 @@
 FILE_PATTERNS = *.h *.m
 HTML_OUTPUT = .
 GENERATE_LATEX = NO
 HIDE_UNDOC_CLASSES = YES
 HIDE_UNDOC_MEMBERS = YES
-PREDEFINED = DOXYGEN			\
-	     OF_HAVE_BLOCKS		\
-	     OF_HAVE_FILES		\
-	     OF_HAVE_SANDBOX		\
-	     OF_HAVE_SOCKETS		\
-	     OF_HAVE_THREADS		\
-	     OF_NO_RETURN		\
-	     OF_NO_RETURN_FUNC		\
-	     OF_NULLABLE_PROPERTY	\
-	     OF_SENTINEL		\
-	     OF_REQUIRES_SUPER		\
-	     OF_RETURNS_RETAINED	\
-	     OF_RETURNS_NOT_RETAINED	\
-	     OF_RETURNS_INNER_POINTER	\
-	     OF_ROOT_CLASS		\
-	     OF_CONSUMED		\
+PREDEFINED = DOXYGEN				\
+	     OF_CONSUMED			\
+	     OF_HAVE_BLOCKS			\
+	     OF_HAVE_FILES			\
+	     OF_HAVE_SANDBOX			\
+	     OF_HAVE_SOCKETS			\
+	     OF_HAVE_THREADS			\
+	     OF_NO_RETURN			\
+	     OF_NO_RETURN_FUNC			\
+	     OF_NULLABLE_PROPERTY		\
+	     OF_NULL_RESETTABLE_PROPERTY	\
+	     OF_REQUIRES_SUPER			\
+	     OF_RETURNS_INNER_POINTER		\
+	     OF_RETURNS_NOT_RETAINED		\
+	     OF_RETURNS_RETAINED		\
+	     OF_ROOT_CLASS			\
+	     OF_SENTINEL			\
 	     OF_WEAK_UNAVAILABLE
 MACRO_EXPANSION = YES
 EXPAND_ONLY_PREDEF = YES
 IGNORE_PREFIX = OF of_

Index: src/macros.h
==================================================================
--- src/macros.h
+++ src/macros.h
@@ -166,17 +166,19 @@
 
 #if __has_feature(nullability)
 # define OF_ASSUME_NONNULL_BEGIN _Pragma("clang assume_nonnull begin")
 # define OF_ASSUME_NONNULL_END _Pragma("clang assume_nonnull end")
 # define OF_NULLABLE_PROPERTY(...) (__VA_ARGS__, nullable)
+# define OF_NULL_RESETTABLE_PROPERTY(...) (__VA_ARGS__, null_resettable)
 #else
 # define OF_ASSUME_NONNULL_BEGIN
 # define OF_ASSUME_NONNULL_END
 # define _Nonnull
 # define _Nullable
 # define _Null_unspecified
 # define OF_NULLABLE_PROPERTY
+# define OF_NULL_RESETTABLE_PROPERTY
 # define nonnull
 # define nullable
 #endif
 
 #if __has_feature(objc_kindof)