diff --git a/eopayment/paybox.py b/eopayment/paybox.py
index 0d3cf2d..acdf2bf 100644
--- a/eopayment/paybox.py
+++ b/eopayment/paybox.py
@@ -137,6 +137,7 @@ class Payment(PaymentCommon):
            production     194.2.160.66  194.2.122.158
            backup         195.25.7.146  195.25.7.166
     '''
+    callback = None
 
     description = {
         'caption': _('Paybox'),
@@ -184,6 +185,10 @@ class Payment(PaymentCommon):
                     ('978', 'Euro'),
                 ),
             },
+            {
+                'name': 'callback',
+                'caption': _('Callback URL'),
+            },
         ]
     }
 
@@ -204,8 +209,8 @@ class Payment(PaymentCommon):
         d['PBX_TIME'] = kwargs.get('time') or (unicode(datetime.datetime.utcnow().isoformat('T')).split('.')[0]+'+00:00')
         d['PBX_ERRORCODETEST'] = '77777'
         d['PBX_ARCHIVAGE'] = transaction_id
-        if 'callback' in kwargs:
-            d['PBX_REPONDRE_A'] = unicode(kwargs['callback'])
+        if self.callback:
+            d['PBX_REPONDRE_A'] = unicode(self.callback)
         d = d.items()
         d = sign(d, self.shared_secret.decode('hex'))
         url = URLS[self.platform]
diff --git a/tests/paybox.py b/tests/paybox.py
index f26b520..9b76e99 100644
--- a/tests/paybox.py
+++ b/tests/paybox.py
@@ -33,6 +33,7 @@ class PayboxTests(TestCase):
             'rang': '001',
             'identifiant': '413536281',
             'shared_secret': key,
+            'callback': 'http://example.com/callback',
         })
         time = '2015-07-15T18:26:32+02:00'
         email = 'bdauvergne@entrouvert.com'
@@ -64,9 +65,10 @@ class PayboxTests(TestCase):
                     'PBX_TOTAL': '1999',
                     'PBX_DEVISE': '978',
                     'PBX_HASH': 'SHA512',
-                    'PBX_HMAC': '41DF99DBE6EAD9F6E2C82C3560A7407AA90E170D69BE14E526EC0589F54A0351BE4FA8E03BCAF5E36D2A3A1060425ACF2A2DE945B1C8422094A34C1CEF48202C',
+                    'PBX_HMAC': 'BA570AF3F5FBF741D3746A9778DB421A68A339669502E9FB2459D0B01EE9E9A88BD499300E6BCE99F729D8FEEE72BDC2F95521F06D2DA1C0924905D1244C6F17',
                     'PBX_ARCHIVAGE': '1234',
                     'PBX_ERRORCODETEST': '77777',
+                    'PBX_REPONDRE_A': 'http://example.com/callback',
                 }
                 self.assertIn(name, values)
                 self.assertEqual(node.attrib['value'], values[name])