Phaser isometric apply physics to body

[PhasedEvolution]

Hello. I created a empty iso sprite in order to make an hitbox. However I am not being able to set its body to collide with world elements. This is my code:

 

hitboxes = game.add.group(); 
hitbox1 = game.add.isoSprite(0,0,0,null,0,hitboxes);
game.physics.isoArcade.enable(hitbox1);
hitbox1.body.collideWorldBounds = true;
hitbox1.body.setSize(300,300,100,0,0,0);
dude.addChild(hitbox1); 

I see the hitbox but it doesn't collide with anything. Why is that?