diff --git a/tiramisu/option.py b/tiramisu/option.py
index da93102..851872d 100644
--- a/tiramisu/option.py
+++ b/tiramisu/option.py
@@ -857,8 +857,8 @@ class PortOption(Option):
                 raise ValueError(_('invalid port'))
             if not self._min_value <= int(val) <= self._max_value:
                 raise ValueError(_('invalid port, must be an between {0} '
-                                    'and {1}').format(self._min_value,
-                                                    self._max_value))
+                                   'and {1}').format(self._min_value,
+                                                     self._max_value))
 
 
 class NetworkOption(Option):