diff --git a/addons/website_portal/controllers/main.py b/addons/website_portal/controllers/main.py
index a11adac2ab4..05627e83416 100644
--- a/addons/website_portal/controllers/main.py
+++ b/addons/website_portal/controllers/main.py
@@ -60,6 +60,7 @@ class website_account(http.Controller):
         error_message = []
 
         mandatory_billing_fields = ["name", "phone", "email", "street2", "city", "country_id"]
+        optional_billing_fields = ["zipcode", "state_id", "vat", "street"]
 
         # Validation
         for field_name in mandatory_billing_fields:
@@ -86,4 +87,9 @@ class website_account(http.Controller):
         if [err for err in error.values() if err == 'missing']:
             error_message.append(_('Some required fields are empty.'))
 
+        unknown = [k for k in data.iterkeys() if k not in mandatory_billing_fields + optional_billing_fields]
+        if unknown:
+            error['common'] = 'Unknown field'
+            error_message.append("Unknown field '%s'" % ','.join(unknown))
+
         return error, error_message