Help With Taryn's Weapon Ammunition System

[TheOnlyArman]

First off, let it be known that I am not all that keen with scripting.. I'm more of an event-minded individual, and I never could wrap my head around scripting.
the Ammunition system that I'm trying to use is here:
http://rmvxp.com/showthread.php?tid=518

The segment of code in question is below.

Code:

#--------------------------------------------------------------------------
  # * Applying Normal Attack Effects
  #     attacker : battler
  #--------------------------------------------------------------------------
  alias ammo_attack attack_effect
  def attack_effect(attacker)
    if attacker.ammo_used_bool != true
      ammo_attack(attacker)
    else
      full_attack(attacker)
    end  
  end

I keep getting
"Script Ammo System" Line 402: Name Error Occured
undefined method 'attack_effect' for class 'Game_Battler'

In the above Code tags are code lines 398-409, which is the entire "section" in regards to Line 402.

Any idea as to why this isn't working?
Cheers!