diff --git a/Line-Item/Tiered Pricing For Bulk Purchases/script.rb b/Line-Item/Tiered Pricing For Bulk Purchases/script.rb
index c07ecbe..e4d4b54 100644
--- a/Line-Item/Tiered Pricing For Bulk Purchases/script.rb	
+++ b/Line-Item/Tiered Pricing For Bulk Purchases/script.rb	
@@ -111,7 +111,7 @@ def partition(cart)
     items = cart.line_items.select { |item| @selector.match?(item) }
 
     # Group items using the appropriate key.
-    cart.line_items.group_by { |item| group_key(item) }
+    items.group_by { |item| group_key(item) }
   end
 
   private