diff --git a/addons/sale/models/res_partner.py b/addons/sale/models/res_partner.py
index d8875db8234..27a70360d45 100644
--- a/addons/sale/models/res_partner.py
+++ b/addons/sale/models/res_partner.py
@@ -14,8 +14,14 @@ class ResPartner(models.Model):
     sale_warn_msg = fields.Text('Message for Sales Order')
 
     def _compute_sale_order_count(self):
-        SaleOrder = self.env['sale.order']
+        sale_data = self.env['sale.order'].read_group(domain=[('partner_id', 'child_of', self.ids)],
+                                                      fields=['partner_id'], groupby=['partner_id'])
+        # read to keep the child/parent relation while aggregating the read_group result in the loop
+        partner_child_ids = self.read(['child_ids'])
+        mapped_data = dict([(m['partner_id'][0], m['partner_id_count']) for m in sale_data])
         for partner in self:
-            partner.sale_order_count = SaleOrder.search_count([
-                ('partner_id', 'child_of', partner.ids)
-            ])
+            # let's obtain the partner id and all its child ids from the read up there
+            partner_ids = filter(lambda r: r['id'] == partner.id, partner_child_ids)[0]
+            partner_ids = [partner_ids.get('id')] + partner_ids.get('child_ids')
+            # then we can sum for all the partner's child
+            partner.sale_order_count = sum(mapped_data.get(child, 0) for child in partner_ids)