diff --git a/invoice.py b/invoice.py
index 74f98f0de7..55d463c102 100644
--- a/invoice.py
+++ b/invoice.py
@@ -88,8 +88,8 @@ class Invoice(metaclass=PoolMeta):
 
     @classmethod
     @process_purchase
-    def post(cls, invoices):
-        super(Invoice, cls).post(invoices)
+    def _post(cls, invoices):
+        super()._post(invoices)
 
     @classmethod
     @process_purchase