Changing a Sprites class. [solved]

Hi,

Here is a short demo to illustrate the problem:

function MyActiveClass::onUpdate(%this) {

  // Do stuff
  
  if( ... some logic ...)
    %this.class = "";
}

function MyActiveClass::Create() {

  %sprite = new t2dStaticSprite()
    {
      // ...Initialise some params...
      class = "MyActiveClass";
    };

  return %sprite;
}

Everything works fine so far, the sprite is created and the MyActiveClass::onUpdate is called periodically.
But at some point I don't want this sprite to be active and stop to call the onUpdate callback. My thought was that if I remove/change the class it will no longer call MyActiveClass:onUpdate. But it continues to call onUpdate even after I changed the class name.

How do I remove the onUpdate calls for a single sprite?