diff --git a/addons/account/report/account_invoice_report.py b/addons/account/report/account_invoice_report.py
index 3930b164f40..4c291cdaf36 100644
--- a/addons/account/report/account_invoice_report.py
+++ b/addons/account/report/account_invoice_report.py
@@ -132,15 +132,7 @@ class account_invoice_report(osv.osv):
                 SELECT min(ail.id) AS id,
                     ai.date_invoice AS date,
                     ail.product_id, ai.partner_id, ai.payment_term, ai.period_id,
-                    CASE
-                     WHEN u.uom_type::text <> 'reference'::text
-                        THEN ( SELECT product_uom.name
-                               FROM product_uom
-                               WHERE product_uom.uom_type::text = 'reference'::text
-                                AND product_uom.active
-                                AND product_uom.category_id = u.category_id LIMIT 1)
-                        ELSE u.name
-                    END AS uom_name,
+                    u2.name AS uom_name,
                     ai.currency_id, ai.journal_id, ai.fiscal_position, ai.user_id, ai.company_id,
                     count(ail.*) AS nbr,
                     ai.type, ai.state, pt.categ_id, ai.date_due, ai.account_id, ail.account_id AS account_line_id,
@@ -160,11 +152,11 @@ class account_invoice_report(osv.osv):
                         THEN SUM(- ail.price_subtotal)
                         ELSE SUM(ail.price_subtotal)
                     END / CASE
-                           WHEN SUM(ail.quantity / u.factor) <> 0::numeric
+                           WHEN SUM(ail.quantity / u.factor * u2.factor) <> 0::numeric
                                THEN CASE
                                      WHEN ai.type::text = ANY (ARRAY['out_refund'::character varying::text, 'in_invoice'::character varying::text])
-                                        THEN SUM((- ail.quantity) / u.factor)
-                                        ELSE SUM(ail.quantity / u.factor)
+                                        THEN SUM((- ail.quantity) / u.factor * u2.factor)
+                                        ELSE SUM(ail.quantity / u.factor * u2.factor)
                                     END
                                ELSE 1::numeric
                           END AS price_average,
@@ -196,17 +188,17 @@ class account_invoice_report(osv.osv):
                 LEFT JOIN product_product pr ON pr.id = ail.product_id
                 left JOIN product_template pt ON pt.id = pr.product_tmpl_id
                 LEFT JOIN product_uom u ON u.id = ail.uos_id
-                LEFT JOIN product_uom u2 ON u.id = pt.uom_id
+                LEFT JOIN product_uom u2 ON u2.id = pt.uom_id
         """
         return from_str
 
     def _group_by(self):
         group_by_str = """
                 GROUP BY ail.product_id, ai.date_invoice, ai.id,
-                    ai.partner_id, ai.payment_term, ai.period_id, u.name, ai.currency_id, ai.journal_id,
+                    ai.partner_id, ai.payment_term, ai.period_id, u2.name, u2.id, ai.currency_id, ai.journal_id,
                     ai.fiscal_position, ai.user_id, ai.company_id, ai.type, ai.state, pt.categ_id,
                     ai.date_due, ai.account_id, ail.account_id, ai.partner_bank_id, ai.residual,
-                    ai.amount_total, u.uom_type, u.category_id, ai.commercial_partner_id, partner.country_id
+                    ai.amount_total, ai.commercial_partner_id, partner.country_id
         """
         return group_by_str