diff --git a/commission.py b/commission.py
index 46f489cdc2..0a808a1def 100644
--- a/commission.py
+++ b/commission.py
@@ -335,10 +335,7 @@ class Commission(ModelSQL, ModelView):
             'in': 'out',
             'out': 'in',
             }.get(self.type_)
-        document = 'invoice' if self.amount > 0 else 'credit_note'
-        return (('agent', self.agent),
-            ('type', '%s_%s' % (direction, document)),
-            )
+        return (('agent', self.agent), ('type', direction))
 
     @classmethod
     def get_journal(cls):
@@ -357,7 +354,7 @@ class Commission(ModelSQL, ModelView):
         Invoice = pool.get('account.invoice')
 
         agent = key['agent']
-        if key['type'].startswith('out'):
+        if key['type'] == 'out':
             payment_term = agent.party.customer_payment_term
         else:
             payment_term = agent.party.supplier_payment_term
@@ -381,7 +378,7 @@ class Commission(ModelSQL, ModelView):
         InvoiceLine = pool.get('account.invoice.line')
 
         def sign(commission):
-            if invoice.type.startswith(commission.type_):
+            if invoice.type == commission.type_:
                 return -1
             else:
                 return 1
@@ -390,9 +387,6 @@ class Commission(ModelSQL, ModelView):
         amount = invoice.currency.round(
             sum(c.amount * sign(c) for c in commissions))
 
-        if invoice.type.endswith('credit_note'):
-            amount *= -1
-
         invoice_line = InvoiceLine()
         invoice_line.invoice = invoice
         invoice_line.type = 'line'
diff --git a/invoice.py b/invoice.py
index 1e50e2fce3..cfad166cb8 100644
--- a/invoice.py
+++ b/invoice.py
@@ -115,10 +115,8 @@ class InvoiceLine:
             ],
         states={
             'invisible': If(Bool(Eval('_parent_invoice')),
-                Eval('_parent_invoice', {}).get('type').in_(
-                    ['in_invoice', 'in_credit_note']),
-                Eval('invoice_type').in_(
-                    ['in_invoice', 'in_credit_note'])),
+                Eval('_parent_invoice', {}).get('type') == 'in',
+                Eval('invoice_type') == 'in'),
             }, depends=['invoice_type', 'company'])
     commissions = fields.One2Many('commission', 'origin', 'Commissions',
         readonly=True,
diff --git a/sale.py b/sale.py
index 36a7ddbabc..162c464428 100644
--- a/sale.py
+++ b/sale.py
@@ -22,8 +22,8 @@ class Sale:
             },
         depends=['state', 'company'])
 
-    def create_invoice(self, invoice_type):
-        invoice = super(Sale, self).create_invoice(invoice_type)
+    def create_invoice(self):
+        invoice = super(Sale, self).create_invoice()
         if invoice:
             invoice.agent = self.agent
             invoice.save()
@@ -39,8 +39,8 @@ class SaleLine:
             ('company', '=', Eval('_parent_sale', {}).get('company', -1)),
             ])
 
-    def get_invoice_line(self, invoice_type):
-        lines = super(SaleLine, self).get_invoice_line(invoice_type)
+    def get_invoice_line(self):
+        lines = super(SaleLine, self).get_invoice_line()
         if self.principal:
             for line in lines:
                 if line.product == self.product:
diff --git a/tests/scenario_commission.rst b/tests/scenario_commission.rst
index 1f9470f937..65c7a4e9b5 100644
--- a/tests/scenario_commission.rst
+++ b/tests/scenario_commission.rst
@@ -175,7 +175,7 @@ Create commission invoices::
     >>> create_invoice.execute('create_')
 
     >>> invoice, = Invoice.find([
-    ...         ('type', '=', 'in_invoice'),
+    ...         ('type', '=', 'in'),
     ...         ])
     >>> invoice.total_amount
     Decimal('10.00')
@@ -186,7 +186,7 @@ Create commission invoices::
     True
 
     >>> invoice, = Invoice.find([
-    ...         ('type', '=', 'out_invoice'),
+    ...         ('type', '=', 'out'),
     ...         ('party', '=', principal.party.id),
     ...         ])
     >>> invoice.total_amount