diff --git a/addons/account/report/account_invoice_report.py b/addons/account/report/account_invoice_report.py
index b7fb9766bf1..efc3c6237bd 100644
--- a/addons/account/report/account_invoice_report.py
+++ b/addons/account/report/account_invoice_report.py
@@ -112,11 +112,7 @@ class account_invoice_report(osv.osv):
                         else
                          ail.quantity*ail.price_unit
                         end) as price_total,
-                    sum(case when ai.type in ('out_refund','in_invoice') then
-                         ail.quantity*ail.price_unit * -1
-                        else
-                         ail.quantity*ail.price_unit
-                        end) / sum(ail.quantity * u.factor)*count(ail.product_id)::decimal(16,2) as price_average,
+                    sum(ail.quantity*ail.price_unit)/sum(ail.quantity*u.factor)*count(ail.product_id)::decimal(16,2) as price_average,
                     sum((select extract(epoch from avg(aml.date_created-l.create_date))/(24*60*60)::decimal(16,2)
                         from account_move_line as aml
                         left join account_invoice as a ON (a.move_id=aml.move_id)