diff --git a/account_credit_control/account.py b/account_credit_control/account.py
index d09b646f6..edaac3e17 100644
--- a/account_credit_control/account.py
+++ b/account_credit_control/account.py
@@ -42,35 +42,3 @@ class AccountAccount(orm.Model):
         default['credit_control_line_ids'] = False
         return super(AccountAccount, self).copy_data(
             cr, uid, id, default=default, context=context)
-
-
-class AccountInvoice(orm.Model):
-    """Add a link to a credit control policy on account.account"""
-
-    _inherit = "account.invoice"
-    _columns = {
-        'credit_policy_id':
-            fields.many2one('credit.control.policy',
-                            'Credit Control Policy',
-                            help=("The Credit Control Policy used for this "
-                                  "invoice. If nothing is defined, it will "
-                                  "use the account setting or the partner "
-                                  "setting."),
-                            readonly=True,
-                            ),
-        'credit_control_line_ids':
-            fields.one2many('credit.control.line',
-                            'invoice_id',
-                            string='Credit Lines',
-                            readonly=True),
-        }
-
-    def copy_data(self, cr, uid, id, default=None, context=None):
-        if default is None:
-            default = {}
-        else:
-            default = default.copy()
-        default = default.copy()
-        default['credit_control_line_ids'] = False
-        return super(AccountInvoice, self).copy_data(
-            cr, uid, id, default=default, context=context)
diff --git a/account_credit_control/invoice.py b/account_credit_control/invoice.py
index c296854ea..98b730b11 100644
--- a/account_credit_control/invoice.py
+++ b/account_credit_control/invoice.py
@@ -26,7 +26,36 @@ class AccountInvoice(orm.Model):
     """Check on cancelling of an invoice"""
     _inherit = 'account.invoice'
 
+    _columns = {
+        'credit_policy_id':
+            fields.many2one('credit.control.policy',
+                            'Credit Control Policy',
+                            help=("The Credit Control Policy used for this "
+                                  "invoice. If nothing is defined, it will "
+                                  "use the account setting or the partner "
+                                  "setting."),
+                            readonly=True,
+                            ),
+        'credit_control_line_ids':
+            fields.one2many('credit.control.line',
+                            'invoice_id',
+                            string='Credit Lines',
+                            readonly=True),
+        }
+
+    def copy_data(self, cr, uid, id, default=None, context=None):
+        """Ensure that credit lines are not duplicated when copy"""
+        if default is None:
+            default = {}
+        else:
+            default = default.copy()
+        default = default.copy()
+        default['credit_control_line_ids'] = False
+        return super(AccountInvoice, self).copy_data(
+            cr, uid, id, default=default, context=context)
+
     def action_cancel(self, cr, uid, ids, context=None):
+        """Prevent to cancel invoice related to credit line"""
         # We will search if this invoice is linked with credit
         cc_line_obj = self.pool.get('credit.control.line')
         for invoice_id in ids: