Imagebutton one on top of the other cannot click one below the other - Scene2d LIBGDX

I have two ImageButtons one on top of the other. Depending on the events in my game, I fadeOut one of the buttons and fadeIn the other, and vice versa. The problem is that buttons are pushed onto the stack at exactly the same position and the button at the bottom doesn't receive the click event. How can I temporarily stack it on top of another that is fading? So does it receive a click event?