Update qbo_invoice.rb

app/models/qbo_invoice.rb

@@ -10,10 +10,13 @@
 
 class QboInvoice < ActiveRecord::Base
   unloadable
+  
   has_and_belongs_to_many :issues
   attr_accessible :doc_number
   validates_presence_of :id, :doc_number
   
+  self.primary_key = :id
+  
   def self.get_base
     Qbo.get_base(:invoice)
   end