Bug in NSJSONSerialization

gistfile1.m

//
//  main.m
//  JSONTrouble
//
//  Created by Roustem Karimov on 11-08-31.
//  Copyright (c) 2011 AgileBits. All rights reserved.
//

#import <Foundation/Foundation.h>

int main (int argc, const char * argv[])
{

	@autoreleasepool {
		/*
		 * Everything works as expected with a non-empty container.
		 */
		NSMutableArray *array1 = [NSMutableArray arrayWithCapacity:2];
		[array1 addObject:@"Hello, World!"];
		NSData *json = [NSJSONSerialization dataWithJSONObject:array1 options:0 error:NULL];
		
		NSMutableArray *array2 = [NSJSONSerialization JSONObjectWithData:json options:NSJSONReadingMutableContainers error:NULL];
		NSLog(@"array1: %@, array2: %@", [array1 className], [array2 className]);

		assert([array2 isKindOfClass:[NSMutableArray class]]); // no problem here
		
		/*
		 * Break when using an empty container.
		 */
		[array1 removeAllObjects];
		json = [NSJSONSerialization dataWithJSONObject:array1 options:0 error:NULL];
		array2 = [NSJSONSerialization JSONObjectWithData:json options:NSJSONReadingMutableContainers error:NULL];
		
		NSLog(@"array1: %@, array2: %@", [array1 className], [array2 className]);
		
		assert([array2 isKindOfClass:[NSMutableArray class]]); // Yay, bug!
	}
	
    return 0;
}