Index: Doxyfile
==================================================================
--- Doxyfile
+++ Doxyfile
@@ -5,10 +5,11 @@
 HTML_OUTPUT = .
 GENERATE_LATEX = NO
 HIDE_UNDOC_CLASSES = YES
 HIDE_UNDOC_MEMBERS = YES
 PREDEFINED = DOXYGEN				\
+	     OF_BOXABLE				\
 	     OF_CONSUMED			\
 	     OF_DESIGNATED_INITIALIZER		\
 	     OF_GENERIC(...)=			\
 	     OF_HAVE_BLOCKS			\
 	     OF_HAVE_FILES			\

Index: src/OFHTTPRequest.h
==================================================================
--- src/OFHTTPRequest.h
+++ src/OFHTTPRequest.h
@@ -53,11 +53,11 @@
  * @struct of_http_request_protocol_version_t \
  *	   OFHTTPRequest.h ObjFW/OFHTTPRequest.h
  *
  * @brief The HTTP version of the HTTP request.
  */
-typedef struct {
+typedef struct OF_BOXABLE {
 	/*! The major of the HTTP version */
 	uint8_t major;
 	/*! The minor of the HTTP version */
 	uint8_t minor;
 } of_http_request_protocol_version_t;

Index: src/OFObject.h
==================================================================
--- src/OFObject.h
+++ src/OFObject.h
@@ -74,11 +74,11 @@
 /*!
  * @struct of_range_t OFObject.h ObjFW/OFObject.h
  *
  * @brief A range.
  */
-typedef struct {
+typedef struct OF_BOXABLE {
 	/*! The start of the range */
 	size_t location;
 	/*! The length of the range */
 	size_t length;
 } of_range_t;
@@ -106,11 +106,11 @@
 /*!
  * @struct of_point_t OFObject.h ObjFW/OFObject.h
  *
  * @brief A point.
  */
-typedef struct {
+typedef struct OF_BOXABLE {
 	/*! The x coordinate of the point */
 	float x;
 	/*! The y coordinate of the point */
 	float y;
 } of_point_t;
@@ -133,11 +133,11 @@
 /*!
  * @struct of_dimension_t OFObject.h ObjFW/OFObject.h
  *
  * @brief A dimension.
  */
-typedef struct {
+typedef struct OF_BOXABLE {
 	/*! The width of the dimension */
 	float width;
 	/*! The height of the dimension */
 	float height;
 } of_dimension_t;
@@ -160,11 +160,11 @@
 /*!
  * @struct of_rectangle_t OFObject.h ObjFW/OFObject.h
  *
  * @brief A rectangle.
  */
-typedef struct {
+typedef struct OF_BOXABLE {
 	/*! The point from where the rectangle originates */
 	of_point_t origin;
 	/*! The size of the rectangle */
 	of_dimension_t size;
 } of_rectangle_t;

Index: src/OFOptionsParser.h
==================================================================
--- src/OFOptionsParser.h
+++ src/OFOptionsParser.h
@@ -25,11 +25,11 @@
 /*!
  * @struct of_options_parser_option_t OFOptionsParser.h ObjFW/OFOptionsParser.h
  *
  * @brief An option which can be parsed by an @ref OFOptionsParser.
  */
-typedef struct of_options_parser_option_t {
+typedef struct {
 	/*! The short version (e.g. `-v`) of the option or `\0` for none. */
 	of_unichar_t shortOption;
 
 	/*!
 	 * The long version (e.g. `--verbose`) of the option or `nil` for none.

Index: src/OFUDPSocket.h
==================================================================
--- src/OFUDPSocket.h
+++ src/OFUDPSocket.h
@@ -29,11 +29,11 @@
 /*!
  * @struct of_udp_socket_address_t OFUDPSocket.h ObjFW/OFUDPSocket.h
  *
  * @brief A struct which represents a host / port pair for a UDP socket.
  */
-typedef struct {
+typedef struct OF_BOXABLE {
 	struct sockaddr_storage address;
 	socklen_t length;
 } of_udp_socket_address_t;
 
 #ifdef OF_HAVE_BLOCKS

Index: src/macros.h
==================================================================
--- src/macros.h
+++ src/macros.h
@@ -268,10 +268,16 @@
 # define OF_DESIGNATED_INITIALIZER \
     __attribute__((__objc_designated_initializer__))
 #else
 # define OF_DESIGNATED_INITIALIZER
 #endif
+
+#if __has_attribute(__objc_boxable__)
+# define OF_BOXABLE __attribute__((__objc_boxable__))
+#else
+# define OF_BOXABLE
+#endif
 
 #if __has_attribute(__swift_name__)
 # define OF_SWIFT_NAME(name) __attribute__((__swift_name__(name)))
 #else
 # define OF_SWIFT_NAME(name)