Index: src/OFBlock.m
==================================================================
--- src/OFBlock.m
+++ src/OFBlock.m
@@ -45,12 +45,12 @@
 	int reserved;
 	void (*invoke)(void *block, ...);
 	struct {
 		unsigned long reserved;
 		unsigned long size;
-		void (*_Nullable copyHelper)(void *dest, void *src);
-		void (*_Nullable disposeHelper)(void *src);
+		void (*copyHelper)(void *dest, void *src);
+		void (*disposeHelper)(void *src);
 		const char *signature;
 	} *descriptor;
 };
 
 struct Byref {

Index: src/OFList.m
==================================================================
--- src/OFList.m
+++ src/OFList.m
@@ -35,13 +35,12 @@
 
 OF_DIRECT_MEMBERS
 @interface OFListEnumerator: OFEnumerator
 {
 	OFList *_list;
-	OFListItem _Nullable _current;
-	unsigned long _mutations;
-	unsigned long *_Nullable _mutationsPtr;
+	OFListItem _current;
+	unsigned long _mutations, *_mutationsPtr;
 }
 
 - (instancetype)initWithList: (OFList *)list
 	    mutationsPointer: (unsigned long *)mutationsPtr;
 @end

Index: src/OFNotificationCenter.m
==================================================================
--- src/OFNotificationCenter.m
+++ src/OFNotificationCenter.m
@@ -332,18 +332,18 @@
 
 	objc_autoreleasePoolPop(pool);
 }
 
 - (void)postNotificationName: (OFNotificationName)name
-		      object: (nullable id)object
+		      object: (id)object
 {
 	[self postNotificationName: name object: object userInfo: nil];
 }
 
 - (void)postNotificationName: (OFNotificationName)name
-		      object: (nullable id)object
-		    userInfo: (nullable OFDictionary *)userInfo
+		      object: (id)object
+		    userInfo: (OFDictionary *)userInfo
 {
 	void *pool = objc_autoreleasePoolPush();
 
 	[self postNotification:
 	    [OFNotification notificationWithName: name

Index: src/OFObject.m
==================================================================
--- src/OFObject.m
+++ src/OFObject.m
@@ -72,11 +72,11 @@
 # include <proto/exec.h>
 # undef Class
 #endif
 
 #ifdef OF_APPLE_RUNTIME
-extern id _Nullable _objc_rootAutorelease(id _Nullable object);
+extern id _objc_rootAutorelease(id object);
 #endif
 #if defined(OF_HAVE_FORWARDING_TARGET_FOR_SELECTOR)
 extern id OFForward(id, SEL, ...);
 extern struct Stret OFForward_stret(id, SEL, ...);
 #else

Index: src/OFSocket.m
==================================================================
--- src/OFSocket.m
+++ src/OFSocket.m
@@ -1050,11 +1050,11 @@
 		@throw [OFInvalidArgumentException exception];
 	}
 }
 
 OFString *
-OFSocketAddressUNIXPath(const OFSocketAddress *_Nonnull address)
+OFSocketAddressUNIXPath(const OFSocketAddress *address)
 {
 	socklen_t length;
 
 	if (address->family != OFSocketAddressFamilyUNIX)
 		@throw [OFInvalidArgumentException exception];

Index: src/exceptions/OFBindIPXSocketFailedException.m
==================================================================
--- src/exceptions/OFBindIPXSocketFailedException.m
+++ src/exceptions/OFBindIPXSocketFailedException.m
@@ -33,11 +33,11 @@
 	OF_UNRECOGNIZED_SELECTOR
 }
 
 + (instancetype)
     exceptionWithNetwork: (uint32_t)network
-		    node: (const unsigned char [_Nonnull IPX_NODE_LEN])node
+		    node: (const unsigned char [IPX_NODE_LEN])node
 		    port: (uint16_t)port
 	      packetType: (uint8_t)packetType
 		  socket: (id)sock
 		   errNo: (int)errNo
 {
@@ -54,11 +54,11 @@
 	OF_INVALID_INIT_METHOD
 }
 
 - (instancetype)
     initWithNetwork: (uint32_t)network
-	       node: (const unsigned char [_Nonnull IPX_NODE_LEN])node
+	       node: (const unsigned char [IPX_NODE_LEN])node
 	       port: (uint16_t)port
 	 packetType: (uint8_t)packetType
 	     socket: (id)sock
 	      errNo: (int)errNo
 {

Index: src/tls/OFOpenSSLTLSStream.m
==================================================================
--- src/tls/OFOpenSSLTLSStream.m
+++ src/tls/OFOpenSSLTLSStream.m
@@ -320,11 +320,11 @@
 }
 
 -      (bool)stream: (OFStream *)stream
   didReadIntoBuffer: (void *)buffer
 	     length: (size_t)length
-	  exception: (nullable id)exception
+	  exception: (id)exception
 {
 	if (exception == nil) {
 		static const OFTLSStreamErrorCode unknownErrorCode =
 		    OFTLSStreamErrorCodeUnknown;
 		int status;

Index: src/tls/OFSecureTransportTLSStream.m
==================================================================
--- src/tls/OFSecureTransportTLSStream.m
+++ src/tls/OFSecureTransportTLSStream.m
@@ -257,11 +257,11 @@
 }
 
 -      (bool)stream: (OFStream *)stream
   didReadIntoBuffer: (void *)buffer
 	     length: (size_t)length
-	  exception: (nullable id)exception
+	  exception: (id)exception
 {
 	if (exception == nil) {
 		OSStatus status = SSLHandshake(_context);
 
 		if (status == errSSLWouldBlock)