diff --git a/addons/payment_adyen/models/adyen.py b/addons/payment_adyen/models/adyen.py
index 594aef58ca6..32e57ab0a47 100644
--- a/addons/payment_adyen/models/adyen.py
+++ b/addons/payment_adyen/models/adyen.py
@@ -27,7 +27,7 @@ class AcquirerAdyen(osv.Model):
          - yhpp: hosted payment page: pay.shtml for single, select.shtml for multiple
         """
         return {
-            'adyen_form_url': 'https://%s.adyen.com/hpp/pay.shtml' % 'live' if environment == 'prod' else environment,
+            'adyen_form_url': 'https://%s.adyen.com/hpp/pay.shtml' % ('live' if environment == 'prod' else environment),
         }
 
     def _get_providers(self, cr, uid, context=None):