The AnimationClip 'Attack' used by the Animation component 'Knife' must be marked as Legacy.

So yeah, help would be appreciated. This is my script:

 #pragma strict
 
 var TheDammage : int = 50;
 var Distance : float;
 var MaxDistance : float = 1.5;
 
 function Update ()
 {
     if (Input.GetButtonDown("Fire1"))
     {
         animation.Play("Attack");
         var hit : RaycastHit;
         if (Physics.Raycast (transform.position, transform.TransformDirection(Vector3.forward), hit))
         {
             Distance = hit.distance;
             if (Distance < MaxDistance)
             {
                 hit.transform.SendMessage("ApplyDammage", TheDammage, SendMessageOptions.DontRequireReceiver);
             }
         }
     }
 }