iOS custom right navigation bar

I'm trying to set an image for a right bar item in my navigation controller but iOS 6 keeps showing a black glow. I have tried a number of solutions from stack overflow but can't get it to work. The current code I have is this:

UIBarButtonItem *rightItem = [[UIBarButtonItem alloc] initWithImage:[UIImage imageNamed:@"gear"]
                                                              style:UIBarButtonItemStylePlain
                                                             target:self
                                                             action:@selector(someMethod)];
[rightItem setImageInsets:UIEdgeInsetsMake(5, 5, 5, 5)];

[[self navigationItem] setRightBarButtonItem:rightItem];

In iOS7 is looks like this which is what I want: This is how it looks in iOS6