diff --git a/invoice.py b/invoice.py
index e72246b40d..5c6e7b3aaf 100644
--- a/invoice.py
+++ b/invoice.py
@@ -1,10 +1,9 @@
 #This file is part of Tryton.  The COPYRIGHT file at the top level
 #of this repository contains the full copyright notices and license terms.
-
-from trytond.osv import fields, OSV
+from trytond.model import ModelView, ModelSQL, fields
 
 
-class Invoice(OSV):
+class Invoice(ModelSQL, ModelView):
     _name = 'account.invoice'
 
     def write(self, cursor, user, ids, vals, context=None):
@@ -28,7 +27,7 @@ class Invoice(OSV):
 Invoice()
 
 
-class InvoiceLine(OSV):
+class InvoiceLine(ModelSQL, ModelView):
     _name = 'account.invoice.line'
 
     def __init__(self):
diff --git a/purchase.py b/purchase.py
index 66519b2c06..5249e15ba6 100644
--- a/purchase.py
+++ b/purchase.py
@@ -1,10 +1,9 @@
 #This file is part of Tryton.  The COPYRIGHT file at the top level
 #of this repository contains the full copyright notices and license terms.
-
-from trytond.osv import fields, OSV
+from trytond.model import ModelView, ModelSQL, fields
 
 
-class Purchase(OSV):
+class Purchase(ModelSQL, ModelView):
     _name = 'purchase.purchase'
 
     invoice_lines = fields.Many2Many('account.invoice.line',