Trying to do special damage to BaseCreature.

[Lemke]

Hello guys!
Im trying to do a weapon (crossbow) to do some special damage to BaseCreature.
Im using this code:

public override void OnHit(Mobile attacker, Mobile defender, ref int damage) //On hit trigger
        {
      
            if (defender is BaseCreature)
            {
            damage = damage * 4;  // Change multiplier here as you wish
            }
            base.OnHit(attacker, defender, ref damage);
        }

But getting error:

Custom/RepeatingCrossboww.cs:
    CS0115: Line 25: 'Server.Items.DaemonicCrossbow.OnHit(Server.Mobile, Server.Mobile, ref int)': no se encontró ningún miembro adecuado que invalidar
Scripts: One or more scripts failed to compile or no script files were found.

Can anyone help?Thanks ina dvance!