How to add a Twitter username to an ABRecordRef

foo.m

-(void)addContact{
	ABRecordRef person;

	ABMultiValueRef social = ABMultiValueCreateMutable(kABMultiDictionaryPropertyType);
	ABMultiValueAddValueAndLabel(social, [NSDictionary dictionaryWithObjectsAndKeys:
										  (NSString *)kABPersonSocialProfileServiceTwitter, kABPersonSocialProfileServiceKey,
										  @"justinbieber", kABPersonSocialProfileUsernameKey,
										  nil], kABPersonSocialProfileServiceTwitter, NULL);
	ABRecordSetValue(person, kABPersonSocialProfileProperty, social, NULL);
	CFRelease(social);
}

NSLog(@"%ld", ABMultiValueGetCount(socialMulti)); return 0 value ???