Casting animation

[Mechanical Man]

How can I change an animation of a caster when casting a certain ability. For example, a unit(model) has an animation 'spell second', but the ability has in 'Animation names' field in object editor a value of 'spell slam'. Even though I change that field with 'spell second' the unit is still using 'spell slam' for that ability. I don't understand why the animation won't change.