diff --git a/tiramisu/config.py b/tiramisu/config.py
index ff8b9cc..548ef94 100644
--- a/tiramisu/config.py
+++ b/tiramisu/config.py
@@ -117,7 +117,7 @@ class Config(object):
             return setattr(homeconfig, name, value)
         if type(getattr(self._cfgimpl_descr, name)) != SymLinkOption:
             self._validate(name, getattr(self._cfgimpl_descr, name))
-        self.setoption(name, value, owners.user)
+        self.setoption(name, value, settings.get_owner())
 
     def _validate(self, name, opt_or_descr, permissive=False):
         "validation for the setattr and the getattr"
@@ -355,7 +355,7 @@ class Config(object):
                     pass
                 except Exception, e:
                     raise e # HiddenOptionError or DisabledOptionError
-                homeconfig.setoption(name, value, owners.user)
+                homeconfig.setoption(name, value, settings.get_owner())
             elif len(candidates) > 1:
                 raise AmbigousOptionError(
                     'more than one option that ends with %s' % (key, ))
diff --git a/tiramisu/option.py b/tiramisu/option.py
index 989d4ba..9dea2e9 100644
--- a/tiramisu/option.py
+++ b/tiramisu/option.py
@@ -65,7 +65,7 @@ class Multi(list):
             super(Multi, self).__init__(lst)
 
     def __setitem__(self, key, value):
-        return self._setvalue(value, key, who=owners.user)
+        return self._setvalue(value, key, who=settings.get_owner())
 
     def append(self, value, add_master=True):
         """the list value can be updated (appened)
@@ -79,14 +79,14 @@ class Multi(list):
                 raise IndexError("in a group with a master, you mustn't add "
                         "a value in a slave's Multi value")
         except TypeError:
-            return self._setvalue(value, who=settings.owner)
+            return self._setvalue(value, who=settings.get_owner())
         multis = []
         for name, multi in self.config:
             multis.append(multi)
         for multi in multis:
             if master == multi.opt._name:
                 if add_master:
-                    ret = multi._setvalue(value, who=settings.owner)
+                    ret = multi._setvalue(value, who=settings.get_owner())
                 else:
                     ret = value
             else:
@@ -99,13 +99,16 @@ class Multi(list):
             if not self.opt._validate(value):
                 raise ConfigError("invalid value {0} "
                     "for option {1}".format(str(value), self.opt._name))
+        if not isinstance(who, owners.Owner):
+            raise TypeError("invalid owner {0} for the value {1}".format(
+                            str(who), str(value)))
         oldvalue = list(self)
         if key is None:
             ret = super(Multi, self).append(value)
         else:
             ret = super(Multi, self).__setitem__(key, value)
         if who != None:
-            self.opt.setowner(self.config, who)
+            self.opt.setowner(self.config, getattr(owners, who))
         self.config._cfgimpl_previous_values[self.opt._name] = oldvalue
         return ret
 
@@ -140,7 +143,7 @@ class Multi(list):
     def _pop(self, key, change_who=True):
         oldvalue = list(self)
         if change_who:
-            self.opt.setowner(self.config, settings.owner)
+            self.opt.setowner(self.config, settings.get_owner())
         self.config._cfgimpl_previous_values[self.opt._name] = oldvalue
         return super(Multi, self).pop(key)
 # ____________________________________________________________
@@ -331,7 +334,7 @@ class Option(HiddenBaseType, DisabledBaseType):
                        (not the toplevel config)
         :return: boolean
         """
-        return self.getowner(config) == 'default'
+        return self.getowner(config) == owners.default
 
     def setoption(self, config, value):
         """changes the option's value with the value_owner's who
diff --git a/tiramisu/setting.py b/tiramisu/setting.py
index dedf27a..431589d 100644
--- a/tiramisu/setting.py
+++ b/tiramisu/setting.py
@@ -114,7 +114,10 @@ class Setting():
     frozen = True
     # enables validation function for options if set
     validator = False
-    # ____________________________________________________________
+   # generic owner
+    owner = owners.user
+
+    #____________________________________________________________
     # properties methods
     def has_properties(self):
         "has properties means the Config's properties attribute is not empty"
@@ -134,7 +137,7 @@ class Setting():
         "deletes property propname in the Config's properties attribute"
         if self.has_property(propname):
             self.properties.remove(propname)
-
+    #____________________________________________________________
     def set_permissive(self, permissive):
         if not isinstance(permissive, list):
             raise TypeError('permissive must be a list')
@@ -183,7 +186,12 @@ class Setting():
 
     def set_owner(self, owner):
         ":param owner: sets the default value for owner at the Config level"
+        if not isinstance(owner, owners.Owner):
+            raise TypeError("invalid generic owner {0}".format(str(owner)))
         self.owner = owner
 
+    def get_owner(self):
+        return self.owner
+
 # Setting is actually a singleton
 settings = Setting()