diff --git a/account_credit_control/invoice.py b/account_credit_control/invoice.py
index 805ae560c..361ffa630 100644
--- a/account_credit_control/invoice.py
+++ b/account_credit_control/invoice.py
@@ -18,69 +18,51 @@
 #    along with this program.  If not, see <http://www.gnu.org/licenses/>.
 #
 ##############################################################################
-from openerp.osv import orm, fields
+from openerp import models, fields, api
 from openerp.tools.translate import _
 
 
-class AccountInvoice(orm.Model):
+class AccountInvoice(models.Model):
     """Check on cancelling of an invoice"""
     _inherit = 'account.invoice'
 
-    _columns = {
-        'credit_policy_id': fields.many2one(
-            'credit.control.policy',
-            'Credit Control Policy',
-            help=("The Credit Control Policy used for this "
-                  "invoice. If nothing is defined, it will "
-                  "use the account setting or the partner "
-                  "setting."),
-            readonly=True,
-        ),
-        'credit_control_line_ids': fields.one2many(
-            'credit.control.line',
-            'invoice_id',
-            string='Credit Lines',
-            readonly=True
-        ),
-    }
+    credit_policy_id = fields.Many2one(
+        'credit.control.policy',
+        string='Credit Control Policy',
+        help="The Credit Control Policy used for this "
+             "invoice. If nothing is defined, it will "
+             "use the account setting or the partner "
+             "setting.",
+        readonly=True,
+        copy=False,
+    )
 
-    def copy_data(self, cr, uid, id, default=None, context=None):
-        """Ensure that credit lines and policy are not copied"""
-        if default is None:
-            default = {}
-        else:
-            default = default.copy()
-        default['credit_control_line_ids'] = False
-        default['credit_policy_id'] = False
-        return super(AccountInvoice, self).copy_data(
-            cr, uid, id, default=default, context=context)
+    credit_control_line_ids = fields.One2many(
+        'credit.control.line', 'invoice_id',
+        string='Credit Lines',
+        readonly=True,
+        copy=False,
+    )
 
-    def action_cancel(self, cr, uid, ids, context=None):
+    @api.multi
+    def action_cancel(self):
         """Prevent to cancel invoice related to credit line"""
         # We will search if this invoice is linked with credit
-        cc_line_obj = self.pool.get('credit.control.line')
-        for invoice_id in ids:
-            cc_nondraft_line_ids = cc_line_obj.search(
-                cr, uid,
-                [('invoice_id', '=', invoice_id),
-                 ('state', '!=', 'draft')],
-                context=context)
-            if cc_nondraft_line_ids:
-                raise orm.except_orm(
-                    _('Error!'),
+        cc_line_obj = self.env['credit.control.line']
+        for invoice in self:
+            nondraft_domain = [('invoice_id', '=', invoice.id),
+                               ('state', '!=', 'draft')]
+            cc_nondraft_lines = cc_line_obj.search(nondraft_domain)
+            if cc_nondraft_lines:
+                raise api.Warning(
                     _('You cannot cancel this invoice.\n'
                       'A payment reminder has already been '
                       'sent to the customer.\n'
                       'You must create a credit note and '
                       'issue a new invoice.')
                 )
-            cc_draft_line_ids = cc_line_obj.search(
-                cr, uid,
-                [('invoice_id', '=', invoice_id),
-                 ('state', '=', 'draft')],
-                context=context)
-            cc_line_obj.unlink(cr, uid,
-                               cc_draft_line_ids,
-                               context=context)
-        return super(AccountInvoice, self).action_cancel(cr, uid, ids,
-                                                         context=context)
+            draft_domain = [('invoice_id', '=', invoice.id),
+                            ('state', '=', 'draft')]
+            cc_draft_line = cc_line_obj.search(draft_domain)
+            cc_draft_line.unlink()
+        return super(AccountInvoice, self).action_cancel()