diff --git a/addons/portal_sale/models/__init__.py b/addons/portal_sale/models/__init__.py
index 38e8290fd7b..027397fad5e 100644
--- a/addons/portal_sale/models/__init__.py
+++ b/addons/portal_sale/models/__init__.py
@@ -3,3 +3,4 @@
 
 import mail_mail
 import sale_order
+import account_invoice
diff --git a/addons/portal_sale/models/account_invoice.py b/addons/portal_sale/models/account_invoice.py
new file mode 100644
index 00000000000..99baf30dc85
--- /dev/null
+++ b/addons/portal_sale/models/account_invoice.py
@@ -0,0 +1,34 @@
+# -*- coding: utf-8 -*-
+# Part of Odoo. See LICENSE file for full copyright and licensing details.
+
+from openerp import SUPERUSER_ID
+from openerp.osv import osv
+from openerp import SUPERUSER_ID
+
+
+class account_invoice(osv.Model):
+    _inherit = 'account.invoice'
+
+    def invoice_validate(self, cr, uid, ids, context=None):
+        # fetch the partner's id and subscribe the partner to the invoice
+        for invoice in self.browse(cr, uid, ids, context=context):
+            partner = invoice.partner_id
+            if partner not in invoice.message_partner_ids:
+                self.message_subscribe(cr, uid, [invoice.id], [partner.id], context=context)
+        return super(account_invoice, self).invoice_validate(cr, uid, ids, context=context)
+
+    def get_signup_url(self, cr, uid, ids, context=None):
+        assert len(ids) == 1
+        document = self.browse(cr, uid, ids[0], context=context)
+        contex_signup = dict(context, signup_valid=True)
+        return self.pool['res.partner']._get_signup_url_for_action(
+            cr, uid, [document.partner_id.id], action='/mail/view',
+            model=self._name, res_id=document.id, context=contex_signup,
+        )[document.partner_id.id]
+
+    def get_formview_action(self, cr, uid, id, context=None):
+        context = context or {}
+        user = self.pool['res.users'].browse(cr, SUPERUSER_ID, context.get('uid', uid), context=context)
+        if user.share:
+            return self.pool['ir.actions.act_window'].for_xml_id(cr, uid, 'portal_sale', 'portal_action_invoices', context=context)
+        return super(account_invoice, self).get_formview_action(cr, uid, id, context=context)
diff --git a/addons/portal_sale/models/sale_order.py b/addons/portal_sale/models/sale_order.py
index 3db3deb7dba..3831cfc02ee 100644
--- a/addons/portal_sale/models/sale_order.py
+++ b/addons/portal_sale/models/sale_order.py
@@ -39,31 +39,3 @@ class sale_order(osv.Model):
             action_xmlid = 'action_quotations_portal' if document.state in ('draft', 'sent') else 'action_orders_portal'
             return self.pool['ir.actions.act_window'].for_xml_id(cr, uid, 'portal_sale', action_xmlid, context=context)
         return super(sale_order, self).get_formview_action(cr, uid, id, context=context)
-
-
-class account_invoice(osv.Model):
-    _inherit = 'account.invoice'
-
-    def invoice_validate(self, cr, uid, ids, context=None):
-        # fetch the partner's id and subscribe the partner to the invoice
-        for invoice in self.browse(cr, uid, ids, context=context):
-            partner = invoice.partner_id
-            if partner not in invoice.message_partner_ids:
-                self.message_subscribe(cr, uid, [invoice.id], [partner.id], context=context)
-        return super(account_invoice, self).invoice_validate(cr, uid, ids, context=context)
-
-    def get_signup_url(self, cr, uid, ids, context=None):
-        assert len(ids) == 1
-        document = self.browse(cr, uid, ids[0], context=context)
-        contex_signup = dict(context, signup_valid=True)
-        return self.pool['res.partner']._get_signup_url_for_action(
-            cr, uid, [document.partner_id.id], action='/mail/view',
-            model=self._name, res_id=document.id, context=contex_signup,
-        )[document.partner_id.id]
-
-    def get_formview_action(self, cr, uid, id, context=None):
-        context = context or {}
-        user = self.pool['res.users'].browse(cr, SUPERUSER_ID, context.get('uid', uid), context=context)
-        if user.share:
-            return self.pool['ir.actions.act_window'].for_xml_id(cr, uid, 'portal_sale', 'portal_action_invoices', context=context)
-        return super(account_invoice, self).get_formview_action(cr, uid, id, context=context)