diff --git a/eopayment/common.py b/eopayment/common.py
index 5c65d5a..6c8afa9 100644
--- a/eopayment/common.py
+++ b/eopayment/common.py
@@ -1,11 +1,13 @@
 import os.path
 import os
 import random
+import logging
 from datetime import date
 
 __all__ = [ 'PaymentCommon', 'URL', 'HTML', 'RANDOM' ]
 
 
+LOGGER = logging.getLogger(__name__)
 RANDOM = random.SystemRandom()
 
 URL = 1
@@ -14,6 +16,14 @@ HTML = 2
 class PaymentCommon(object):
     PATH = '/tmp'
 
+    def __init__(self, options):
+        LOGGER.debug('initializing with options %s' % options)
+        for key, value in self.description['parameters'].iteritems():
+            if 'default' in value:
+                setattr(self, key, options.get(key, value['default']))
+            else:
+                setattr(self, key, options.get(key))
+
     def transaction_id(self, length, choices, *prefixes):
         while True:
             parts = [RANDOM.choice(choices) for x in range(length)]
diff --git a/eopayment/dummy.py b/eopayment/dummy.py
index 966835f..3c0b6b4 100644
--- a/eopayment/dummy.py
+++ b/eopayment/dummy.py
@@ -20,10 +20,25 @@ class Payment(PaymentCommon):
        you can find on:
 
            http://dummy-payment.demo.entrouvert.com/
+
+       You must pass the following keys inside the options dictionnary:
+        - dummy_service_url, the URL of the dummy payment service, it defaults
+          to the one operated by Entr'ouvert.
+        - direct_notification_url: where to POST to notify the service of a
+          payment
+        - origin: a human string to display to the user about the origin of
+          the request.
+        - siret: an identifier for the eCommerce site, fake.
+        - next_url: the return URL for the user (can be overriden on a per
+          request basis).
     '''
     description = {
             'caption': 'Dummy payment backend',
             'parameters': {
+                'dummy_service_url': {
+                    'caption': 'URL of the dummy payment service',
+                    'default': SERVICE_URL,
+                },
                 'direct_notification_url': {
                     'caption': 'direct notification url',
                 },
@@ -40,20 +55,6 @@ class Payment(PaymentCommon):
             }
     }
 
-    def __init__(self, options):
-        '''
-           You must pass the following keys inside the options dictionnary:
-            - direct_notification_url: where to POST to notify the service of a
-              payment
-            - siret: an identifier for the eCommerce site
-            - origin: a human string to display to the user about the origin of
-              the request.
-        '''
-        self.direct_notification_url = options['direct_notification_url']
-        self.siret = options['siret']
-        self.origin = options['origin']
-        self.next_url = options.get('next_url','')
-
     def request(self, montant, email=None, next_url=None):
         transaction_id = self.transaction_id(30, ALPHANUM, 'dummy', self.siret)
         if self.next_url:
@@ -87,7 +88,6 @@ if __name__ == '__main__':
             'origin': 'Mairie de Perpette-les-oies'
     }
     p = Payment(options)
-    print p.request(10.00, email='toto@example.com', next_url='http://example.com/retour')
     retour = 'http://example.com/retour?amount=10.0&direct_notification_url=http%3A%2F%2Fexample.com%2Fdirect_notification_url&email=toto%40example.com&transaction_id=6Tfw2e1bPyYnz7CedZqvdHt7T9XX6T&return_url=http%3A%2F%2Fexample.com%2Fretour&nok=1'
     r = p.response(retour.split('?',1)[1])
     assert not r[0] 
diff --git a/eopayment/spplus.py b/eopayment/spplus.py
index f10fc89..5673e60 100644
--- a/eopayment/spplus.py
+++ b/eopayment/spplus.py
@@ -63,17 +63,18 @@ class Payment(PaymentCommon):
                     'caption': 'Siret of the entreprise augmented with the '
                         'site number, example: 00000000000001-01',
                     'regexp': re.compile('^ *(\d{14}-\d{2}) *$')
-                }
+                },
+                'langue': {
+                    'caption': 'Language of the customers',
+                    'default': 'FR',
+                },
+                'taxe': {
+                    'caption': 'Taxes',
+                    'default': '0.00'
+                },
             }
     }
-
-    def __init__(self, options):
-        LOGGER.debug('initializing spplus payment with %s' % options)
-        self.cle = options['cle']
-        self.siret = options['siret']
-        self.devise = '978'
-        self.langue = options.get('langue', 'FR')
-        self.taxe = options.get('taxe', '0.00')
+    devise = '978'
 
     def request(self, montant, email=None, next_url=None):
         LOGGER.debug('requesting spplus payment with montant %s email=%s and \
diff --git a/eopayment/systempayv2.py b/eopayment/systempayv2.py
index 246ff59..1a5a09c 100644
--- a/eopayment/systempayv2.py
+++ b/eopayment/systempayv2.py
@@ -25,8 +25,8 @@ def isonow():
             .replace(':','')[:14]
 
 class Parameter:
-    def __init__(self, name, ptype, code, max_length=None, length=None, needed=False,
-            default=None, choices=None):
+    def __init__(self, name, ptype, code, max_length=None, length=None,
+            needed=False, default=None, choices=None):
         self.name = name
         self.ptype = ptype
         self.code = code