KVO method firing twice

kvotest.j

//Output:
/*
Frameworks/Debug/Objective-J/Objective-J.js:4322011-05-27 20:42:05.282 Cappuccino [info]: observed: attributeController.arrangedObjects change: {
	CPKeyValueChangeKindKey = "1"
	CPKeyValueChangeOldKey = "newArrayObject"
	CPKeyValueChangeNewKey = "newArrayObject"
}
Frameworks/Debug/Objective-J/Objective-J.js:4322011-05-27 20:42:05.284 Cappuccino [info]: observed: attributeController.arrangedObjects change: {
	CPKeyValueChangeKindKey = "1"
	CPKeyValueChangeOldKey = "newArrayObject"
	CPKeyValueChangeNewKey = "newArrayObject"
}

*/

//AppController.j:

/*
 * AppController.j
 * KVOTest
 */

@import <Foundation/CPObject.j>
@import "ParentObject.j"


@implementation AppController : CPObject
{
    CPWindow    theWindow; //this "outlet" is connected automatically by the Cib
    ParentObject testObject @accessors;
    
}

- (void)applicationDidFinishLaunching:(CPNotification)aNotification
{
    // This is called when the application is done loading.
    testObject = [[ParentObject alloc] init];
 
    [testObject addObserver:self
                 forKeyPath:@"attributeController.arrangedObjects"
                    options:(CPKeyValueObservingOptionNew)
                    context:NULL];
    
    [[testObject attributeController] addObject:@"newArrayObject"];
   
}

- (void)awakeFromCib
{
    // This is called when the cib is done loading.
    // You can implement this method on any object instantiated from a Cib.
    // It's a useful hook for setting up current UI values, and other things.

    // In this case, we want the window from Cib to become our full browser window
    [theWindow setFullPlatformWindow:YES];
}

- (void)observeValueForKeyPath:(CPString)keyPath ofObject:(id)object change:(CPDictionary)change context:(void )context
{
    CPLog(@"observed: "+keyPath+" change: "+change);
}

@end

//ParentObject.j:


@import <Foundation/CPObject.j>

@implementation ParentObject : CPObject
{
    CPMutableArray attributeArray @accessors;
    CPArrayController attributeController @accessors;
}

-(id)init
{
    self = [super init];
    if(self)
    {
        attributeArray = [[CPMutableArray alloc] init];
        attributeController = [[CPArrayController alloc] init];
        [attributeController setContent:attributeArray];
    }
    return self;
}


@end