diff --git a/addons/purchase/purchase.py b/addons/purchase/purchase.py
index 79bc59759ae..108d17bfd4b 100644
--- a/addons/purchase/purchase.py
+++ b/addons/purchase/purchase.py
@@ -218,6 +218,9 @@ class purchase_order(osv.osv):
         'pricelist_id': lambda self, cr, uid, context: context.get('partner_id', False) and self.pool.get('res.partner').browse(cr, uid, context['partner_id']).property_product_pricelist_purchase.id,
         'company_id': lambda self,cr,uid,c: self.pool.get('res.company')._company_default_get(cr, uid, 'purchase.order', context=c),
     }
+    _sql_constraints = [
+        ('name_uniq', 'unique(name)', 'Order Reference must be unique !'),
+    ]
     _name = "purchase.order"
     _description = "Purchase Order"
     _order = "name desc"
diff --git a/addons/sale/sale.py b/addons/sale/sale.py
index 29cd5ea593a..2d6fc87a240 100644
--- a/addons/sale/sale.py
+++ b/addons/sale/sale.py
@@ -185,7 +185,7 @@ class sale_order(osv.osv):
         for line in self.pool.get('sale.order.line').browse(cr, uid, ids, context=context):
             result[line.order_id.id] = True
         return result.keys()
-
+    
     _columns = {
         'name': fields.char('Order Reference', size=64, required=True,
             readonly=True, states={'draft': [('readonly', False)]}, select=True),
@@ -274,6 +274,9 @@ class sale_order(osv.osv):
         'partner_order_id': lambda self, cr, uid, context: context.get('partner_id', False) and  self.pool.get('res.partner').address_get(cr, uid, [context['partner_id']], ['contact'])['contact'],
         'partner_shipping_id': lambda self, cr, uid, context: context.get('partner_id', False) and self.pool.get('res.partner').address_get(cr, uid, [context['partner_id']], ['delivery'])['delivery'],
     }
+    _sql_constraints = [
+        ('name_uniq', 'unique(name)', 'Order Reference must be unique !'),
+    ]
     _order = 'name desc'
 
     # Form filling