@@ -161,11 +161,11 @@
 void *
 _Block_copy(const void *block_)
 {
 	of_block_literal_t *block = (of_block_literal_t *)block_;
 
-	if (object_getClass((id)block) == (Class)&_NSConcreteStackBlock) {
+	if ([(id)block isMemberOfClass: (Class)&_NSConcreteStackBlock]) {
 		of_block_literal_t *copy;
 
 		if ((copy = malloc(block->descriptor->size)) == NULL) {
 			alloc_failed_exception.isa =
 			    [OFAllocFailedException class];
@@ -181,11 +181,11 @@
 			block->descriptor->copy_helper(copy, block);
 
 		return copy;
 	}
 
-	if (object_getClass((id)block) == (Class)&_NSConcreteMallocBlock) {
+	if ([(id)block isMemberOfClass: (Class)&_NSConcreteMallocBlock]) {
 #ifdef OF_HAVE_ATOMIC_OPS
 		of_atomic_int_inc(&block->flags);
 #else
 		unsigned hash = SPINLOCK_HASH(block);
 
@@ -464,11 +464,11 @@
 	OF_UNRECOGNIZED_SELECTOR
 }
 
 - (instancetype)retain
 {
-	if (object_getClass(self) == (Class)&_NSConcreteMallocBlock)
+	if ([self isMemberOfClass: (Class)&_NSConcreteMallocBlock])
 		return Block_copy(self);
 
 	return self;
 }
 
@@ -477,31 +477,31 @@
 	return Block_copy(self);
 }
 
 - (instancetype)autorelease
 {
-	if (object_getClass(self) == (Class)&_NSConcreteMallocBlock)
+	if ([self isMemberOfClass: (Class)&_NSConcreteMallocBlock])
 		return [super autorelease];
 
 	return self;
 }
 
 - (unsigned int)retainCount
 {
-	if (object_getClass(self) == (Class)&_NSConcreteMallocBlock)
+	if ([self isMemberOfClass: (Class)&_NSConcreteMallocBlock])
 		return ((of_block_literal_t *)self)->flags &
 		    OF_BLOCK_REFCOUNT_MASK;
 
 	return OF_RETAIN_COUNT_MAX;
 }
 
 - (void)release
 {
-	if (object_getClass(self) == (Class)&_NSConcreteMallocBlock)
+	if ([self isMemberOfClass: (Class)&_NSConcreteMallocBlock])
 		Block_release(self);
 }
 
 - (void)dealloc
 {
 	OF_DEALLOC_UNSUPPORTED
 }
 @end