@@ -139,12 +139,13 @@
 
 	instance = malloc(PRE_IVAR_ALIGN + instanceSize +
 	    extraAlignment + extraSize);
 
 	if (OF_UNLIKELY(instance == nil)) {
-		alloc_failed_exception.isa = [OFAllocFailedException class];
-		@throw (OFAllocFailedException*)&alloc_failed_exception;
+		object_setClass((id)&alloc_failed_exception,
+		    [OFAllocFailedException class]);
+		@throw (id)&alloc_failed_exception;
 	}
 
 	((struct pre_ivar*)instance)->retainCount = 1;
 	((struct pre_ivar*)instance)->firstMem = NULL;
 	((struct pre_ivar*)instance)->lastMem = NULL;
@@ -158,13 +159,12 @@
 	}
 #endif
 
 	instance = (OFObject*)((char*)instance + PRE_IVAR_ALIGN);
 
-	instance->isa = class;
-	memset((char*)instance + sizeof(instance->isa), 0,
-	    instanceSize - sizeof(instance->isa));
+	memset(instance, 0, instanceSize);
+	object_setClass(instance, class);
 
 	if (OF_UNLIKELY(extra != NULL))
 		*extra = (char*)instance + instanceSize + extraAlignment;
 
 	return instance;
@@ -365,11 +365,11 @@
 
 + (IMP)replaceClassMethod: (SEL)selector
        withImplementation: (IMP)implementation
 	     typeEncoding: (const char*)typeEncoding
 {
-	return class_replaceMethod(((OFObject*)self)->isa, selector,
+	return class_replaceMethod(object_getClass(self), selector,
 	    implementation, typeEncoding);
 }
 
 + (void)inheritMethodsFromClass: (Class)class
 {
@@ -380,11 +380,11 @@
 
 #if defined(OF_APPLE_RUNTIME)
 	Method *methodList;
 	unsigned i, count;
 
-	methodList = class_copyMethodList(((OFObject*)class)->isa, &count);
+	methodList = class_copyMethodList(object_getClass(class), &count);
 	@try {
 		for (i = 0; i < count; i++) {
 			SEL selector = method_getName(methodList[i]);
 
 			/*
@@ -420,11 +420,11 @@
 		free(methodList);
 	}
 #elif defined(OF_OBJFW_RUNTIME)
 	struct objc_method_list *methodlist;
 
-	for (methodlist = class->isa->methodlist;
+	for (methodlist = object_getClass(class)->methodlist;
 	    methodlist != NULL; methodlist = methodlist->next) {
 		int i;
 
 		for (i = 0; i < methodlist->count; i++) {
 			SEL selector = (SEL)&methodlist->methods[i].sel;
@@ -467,11 +467,12 @@
 - init
 {
 	Class class;
 	void (*last)(id, SEL) = NULL;
 
-	for (class = isa; class != Nil; class = class_getSuperclass(class)) {
+	for (class = object_getClass(self); class != Nil;
+	    class = class_getSuperclass(class)) {
 		void (*construct)(id, SEL);
 
 		if ([class instancesRespondToSelector: cxx_construct]) {
 			if ((construct = (void(*)(id, SEL))[class
 			    instanceMethodForSelector: cxx_construct]) != last)
@@ -485,48 +486,49 @@
 	return self;
 }
 
 - (Class)class
 {
-	return isa;
+	return object_getClass(self);
 }
 
 - (OFString*)className
 {
-	return [OFString stringWithCString: class_getName(isa)
+	return [OFString stringWithCString: object_getClassName(self)
 				  encoding: OF_STRING_ENCODING_ASCII];
 }
 
 - (BOOL)isKindOfClass: (Class)class
 {
 	Class iter;
 
-	for (iter = isa; iter != Nil; iter = class_getSuperclass(iter))
+	for (iter = object_getClass(self); iter != Nil;
+	    iter = class_getSuperclass(iter))
 		if (iter == class)
 			return YES;
 
 	return NO;
 }
 
 - (BOOL)isMemberOfClass: (Class)class
 {
-	return (isa == class);
+	return (object_getClass(self) == class);
 }
 
 - (BOOL)respondsToSelector: (SEL)selector
 {
-	return class_respondsToSelector(isa, selector);
+	return class_respondsToSelector(object_getClass(self), selector);
 }
 
 - (BOOL)conformsToProtocol: (Protocol*)protocol
 {
-	return [isa conformsToProtocol: protocol];
+	return [object_getClass(self) conformsToProtocol: protocol];
 }
 
 - (IMP)methodForSelector: (SEL)selector
 {
-	return class_getMethodImplementation(isa, selector);
+	return class_getMethodImplementation(object_getClass(self), selector);
 }
 
 - (id)performSelector: (SEL)selector
 {
 	id (*imp)(id, SEL) = (id(*)(id, SEL))[self methodForSelector: selector];
@@ -556,23 +558,26 @@
 - (const char*)typeEncodingForSelector: (SEL)selector
 {
 #if defined(OF_OBJFW_RUNTIME)
 	const char *ret;
 
-	if ((ret = objc_get_type_encoding(isa, selector)) == NULL)
-		@throw [OFNotImplementedException exceptionWithClass: isa
-							    selector: selector];
+	if ((ret = objc_get_type_encoding(object_getClass(self),
+	    selector)) == NULL)
+		@throw [OFNotImplementedException
+		    exceptionWithClass: [self class]
+			      selector: selector];
 
 	return ret;
 #else
 	Method m;
 	const char *ret;
 
-	if ((m = class_getInstanceMethod(isa, selector)) == NULL ||
-	    (ret = method_getTypeEncoding(m)) == NULL)
-		@throw [OFNotImplementedException exceptionWithClass: isa
-							    selector: selector];
+	if ((m = class_getInstanceMethod(object_getClass(self),
+	    selector)) == NULL || (ret = method_getTypeEncoding(m)) == NULL)
+		@throw [OFNotImplementedException
+		    exceptionWithClass: [self class]
+			      selector: selector];
 
 	return ret;
 #endif
 }
 
@@ -598,14 +603,14 @@
 {
 	void *pointer;
 	struct pre_mem *preMem;
 
 	if (size > SIZE_MAX - PRE_IVAR_ALIGN)
-		@throw [OFOutOfRangeException exceptionWithClass: isa];
+		@throw [OFOutOfRangeException exceptionWithClass: [self class]];
 
 	if ((pointer = malloc(PRE_MEM_ALIGN + size)) == NULL)
-		@throw [OFOutOfMemoryException exceptionWithClass: isa
+		@throw [OFOutOfMemoryException exceptionWithClass: [self class]
 						    requestedSize: size];
 	preMem = pointer;
 
 	preMem->owner = self;
 	preMem->prev = PRE_IVAR->lastMem;
@@ -624,11 +629,11 @@
 {
 	if (size == 0 || count == 0)
 		return NULL;
 
 	if (count > SIZE_MAX / size)
-		@throw [OFOutOfRangeException exceptionWithClass: isa];
+		@throw [OFOutOfRangeException exceptionWithClass: [self class]];
 
 	return [self allocMemoryWithSize: size * count];
 }
 
 - (void*)resizeMemory: (void*)pointer
@@ -645,15 +650,15 @@
 		return NULL;
 	}
 
 	if (PRE_MEM(pointer)->owner != self)
 		@throw [OFMemoryNotPartOfObjectException
-		    exceptionWithClass: isa
+		    exceptionWithClass: [self class]
 			       pointer: pointer];
 
 	if ((new = realloc(PRE_MEM(pointer), PRE_MEM_ALIGN + size)) == NULL)
-		@throw [OFOutOfMemoryException exceptionWithClass: isa
+		@throw [OFOutOfMemoryException exceptionWithClass: [self class]
 						    requestedSize: size];
 	preMem = new;
 
 	if (preMem != PRE_MEM(pointer)) {
 		if (preMem->prev != NULL)
@@ -682,11 +687,11 @@
 		[self freeMemory: pointer];
 		return NULL;
 	}
 
 	if (count > SIZE_MAX / size)
-		@throw [OFOutOfRangeException exceptionWithClass: isa];
+		@throw [OFOutOfRangeException exceptionWithClass: [self class]];
 
 	return [self resizeMemory: pointer
 			     size: size * count];
 }
 
@@ -695,11 +700,11 @@
 	if (pointer == NULL)
 		return;
 
 	if (PRE_MEM(pointer)->owner != self)
 		@throw [OFMemoryNotPartOfObjectException
-		    exceptionWithClass: isa
+		    exceptionWithClass: [self class]
 			       pointer: pointer];
 
 	if (PRE_MEM(pointer)->prev != NULL)
 		PRE_MEM(pointer)->prev->next = PRE_MEM(pointer)->next;
 	if (PRE_MEM(pointer)->next != NULL)
@@ -785,11 +790,12 @@
 {
 	Class class;
 	void (*last)(id, SEL) = NULL;
 	struct pre_mem *iter;
 
-	for (class = isa; class != Nil; class = class_getSuperclass(class)) {
+	for (class = object_getClass(self); class != Nil;
+	    class = class_getSuperclass(class)) {
 		void (*destruct)(id, SEL);
 
 		if ([class instancesRespondToSelector: cxx_destruct]) {
 			if ((destruct = (void(*)(id, SEL))[class
 			    instanceMethodForSelector: cxx_destruct]) != last)
@@ -821,21 +827,23 @@
 
 /* Required to use properties with the Apple runtime */
 - copyWithZone: (void*)zone
 {
 	if (zone != NULL)
-		@throw [OFNotImplementedException exceptionWithClass: isa
-							    selector: _cmd];
+		@throw [OFNotImplementedException
+		    exceptionWithClass: [self class]
+			      selector: _cmd];
 
 	return [(id)self copy];
 }
 
 - mutableCopyWithZone: (void*)zone
 {
 	if (zone != NULL)
-		@throw [OFNotImplementedException exceptionWithClass: isa
-							    selector: _cmd];
+		@throw [OFNotImplementedException
+		    exceptionWithClass: [self class]
+			      selector: _cmd];
 
 	return [(id)self mutableCopy];
 }
 
 /*