Opening maps with current location and directions in iOS 6

I am building an app that can open the Maps app with directions from the user's current position to another position. The code looks like this:

- (id)resolveDirectionsFromCoordinate:(CLLocationCoordinate2D)startCoordinate toCoordinate:(CLLocationCoordinate2D)endCoordinate
{
    NSString* url = [NSString stringWithFormat: @"http://maps.google.com/maps?saddr=%f,%f&daddr=%f,%f",
                 startCoordinate.latitude, startCoordinate.longitude,
                 endCoordinate.latitude, endCoordinate.longitude];
    [[UIApplication sharedApplication] openURL: [NSURL URLWithString: url]];

    return nil;
}

Thos works well in iOS 5.x. In iOS 6, however, this brings up Safari instead, since Maps no longer uses Google Maps.

Does anyone know which URL I should call in iOS 6?