diff --git a/addons/account/account.py b/addons/account/account.py
index 18cabe9e169..da19fcf7197 100644
--- a/addons/account/account.py
+++ b/addons/account/account.py
@@ -2141,8 +2141,8 @@ class account_tax(osv.osv):
 
     @api.v8
     def compute_all(self, price_unit, quantity, product=None, partner=None, force_excluded=False):
-        return self._model.compute_all(
-            self._cr, self._uid, self, price_unit, quantity,
+        return account_tax.compute_all(
+            self._model, self._cr, self._uid, self, price_unit, quantity,
             product=product, partner=partner, force_excluded=force_excluded)
 
     def compute(self, cr, uid, taxes, price_unit, quantity,  product=None, partner=None):
diff --git a/addons/account/account_invoice.py b/addons/account/account_invoice.py
index 48f22763986..90d4d7fd954 100644
--- a/addons/account/account_invoice.py
+++ b/addons/account/account_invoice.py
@@ -1209,7 +1209,7 @@ class account_invoice(models.Model):
     def pay_and_reconcile(self, cr, uid, ids, pay_amount, pay_account_id, period_id, pay_journal_id,
                           writeoff_acc_id, writeoff_period_id, writeoff_journal_id, context=None, name=''):
         recs = self.browse(cr, uid, ids, context)
-        return recs.pay_and_reconcile(pay_amount, pay_account_id, period_id, pay_journal_id,
+        return account_invoice.pay_and_reconcile(recs, pay_amount, pay_account_id, period_id, pay_journal_id,
                     writeoff_acc_id, writeoff_period_id, writeoff_journal_id, name=name)
 
 class account_invoice_line(models.Model):
@@ -1600,7 +1600,7 @@ class account_invoice_tax(models.Model):
     def compute(self, cr, uid, invoice_id, context=None):
         recs = self.browse(cr, uid, [], context)
         invoice = recs.env['account.invoice'].browse(invoice_id)
-        return recs.compute(invoice)
+        return account_invoice_tax.compute(recs, invoice)
 
     @api.model
     def move_line_get(self, invoice_id):
diff --git a/addons/report/models/report.py b/addons/report/models/report.py
index 10142ff0695..aa6b6d143b1 100644
--- a/addons/report/models/report.py
+++ b/addons/report/models/report.py
@@ -177,8 +177,8 @@ class Report(osv.Model):
 
     @api.v8
     def get_html(self, records, report_name, data=None):
-        return self._model.get_html(self._cr, self._uid, records.ids, report_name,
-                                    data=data, context=self._context)
+        return Report.get_html(self._model, self._cr, self._uid, records.ids,
+                               report_name, data=data, context=self._context)
 
     @api.v7
     def get_pdf(self, cr, uid, ids, report_name, html=None, data=None, context=None):
@@ -276,8 +276,8 @@ class Report(osv.Model):
 
     @api.v8
     def get_pdf(self, records, report_name, html=None, data=None):
-        return self._model.get_pdf(self._cr, self._uid, records.ids, report_name,
-                                   html=html, data=data, context=self._context)
+        return Report.get_pdf(self._model, self._cr, self._uid, records.ids,
+                              report_name, html=html, data=data, context=self._context)
 
     @api.v7
     def get_action(self, cr, uid, ids, report_name, data=None, context=None):
@@ -313,8 +313,8 @@ class Report(osv.Model):
 
     @api.v8
     def get_action(self, records, report_name, data=None):
-        return self._model.get_action(self._cr, self._uid, records.ids, report_name,
-                                      data=data, context=self._context)
+        return Report.get_action(self._model, self._cr, self._uid, records.ids,
+                                 report_name, data=data, context=self._context)
 
     #--------------------------------------------------------------------------
     # Report generation helpers
@@ -360,8 +360,8 @@ class Report(osv.Model):
 
     @api.v8
     def _check_attachment_use(self, records, report):
-        return self._model._check_attachment_use(
-            self._cr, self._uid, records.ids, report, context=self._context)
+        return Report._check_attachment_use(
+            self._model, self._cr, self._uid, records.ids, report, context=self._context)
 
     def _check_wkhtmltopdf(self):
         return wkhtmltopdf_state
diff --git a/openerp/api.py b/openerp/api.py
index 3602790848b..010299d2a6a 100644
--- a/openerp/api.py
+++ b/openerp/api.py
@@ -608,6 +608,16 @@ def v7(method_v7):
             def foo(self):
                 ...
 
+        Special care must be taken if one method calls the other one, because
+        the method may be overridden! In that case, one should call the method
+        from the current class (say ``MyClass``), for instance::
+
+            @api.v7
+            def foo(self, cr, uid, ids, context=None):
+                # Beware: records.foo() may call an overriding of foo()
+                records = self.browse(cr, uid, ids, context)
+                return MyClass.foo(records)
+
         Note that the wrapper method uses the docstring of the first method.
     """
     # retrieve method_v8 from the caller's frame