diff --git a/app/lib/order_pdf.rb b/app/lib/order_pdf.rb
index 655e5fbe..869cb0e8 100644
--- a/app/lib/order_pdf.rb
+++ b/app/lib/order_pdf.rb
@@ -113,7 +113,7 @@ class OrderPdf < RenderPdf
       # get quantity for each article and ordergroup
       goa_records = group_order_articles(group_ids)
                     .group('group_order_articles.order_article_id, group_orders.ordergroup_id')
-                    .pluck('group_order_articles.order_article_id', 'group_orders.ordergroup_id', 'SUM(COALESCE(group_order_articles.result, group_order_articles.quantity))')
+                    .pluck('group_order_articles.order_article_id', 'group_orders.ordergroup_id', Arel.sql('SUM(COALESCE(group_order_articles.result, group_order_articles.quantity))'))
 
       # transform the flat list of results in a hash (with the article as key), which contains an array for all ordergroups
       results = goa_records.group_by(&:first).transform_values do |value|