Keep iPhone UIButton Highlighted

I have the following code snippets:

@interface Foo: UIViewController {
  ...
  UIButton *myButton;
  ...
}

@implementation Foo

- (void) viewDidLoad {
  ...
  myButton.highlighted = YES;
  ...
}

When I run the app, the button is highlighted in blue (default behavior). It works as I expected.

But after pressing the button once, the button is no longer highlighted.

Then, I created an IBAction highlightButton to handle Touch Up Inside event where I explicitly call myButton.highlighted = Yes;. Unfortunately, the button highlight still does not stay.

How can I keep it highlighted in blue even after being pressed?