diff --git a/app/models/ordergroup.rb b/app/models/ordergroup.rb
index 9b50907e..efaae4de 100644
--- a/app/models/ordergroup.rb
+++ b/app/models/ordergroup.rb
@@ -62,6 +62,7 @@ class Ordergroup < Group
     # Get group_order.price for every finished order in this period
     orders_sum = group_orders.includes(:order).merge(Order.finished).where('orders.ends >= ?', time).sum(:price)
 
+    @readonly = false # Dirty hack, avoid getting RecordReadOnly exception when called in task after_save callback. A rails bug?
     update_attribute(:stats, {:jobs_size => jobs, :orders_sum => orders_sum})
   end
 
diff --git a/app/models/task.rb b/app/models/task.rb
index 3a290e2c..e957d2f1 100644
--- a/app/models/task.rb
+++ b/app/models/task.rb
@@ -99,7 +99,7 @@ class Task < ActiveRecord::Base
 
   def update_ordergroup_stats
     if done
-      users.each { |u| u.ordergroup.update_stats! if u.ordergroup }
+      Ordergroup.joins(:users).where(users: {id: user_ids}).each(&:update_stats!)
     end
   end
 end