Can't get a translucent status bar

Question

Starting out with a default gray status bar, I'm pushing a UIViewController subclass onto a navigation controller stack and calling

    [[UIApplication sharedApplication] setStatusBarStyle:UIStatusBarStyleBlackTranslucent
                                                animated:YES];

during viewWillAppear:. But I get an opaque black status bar instead. Simulator and iPhone. 3.0. Any ideas?