diff --git a/tiramisu/option/baseoption.py b/tiramisu/option/baseoption.py
index 0135ef9..ffdb935 100644
--- a/tiramisu/option/baseoption.py
+++ b/tiramisu/option/baseoption.py
@@ -275,15 +275,10 @@ class Base(object):
             self._val_call = (val, val_call)
 
     def impl_is_optiondescription(self):
-        #FIXME deplacer dans OpenDescription ?
-        return self.__class__.__name__ in ['OptionDescription',
-                                           'DynOptionDescription',
-                                           'SynDynOptionDescription',
-                                           'MasterSlaves']
+        return False
 
     def impl_is_dynoptiondescription(self):
-        return self.__class__.__name__ in ['DynOptionDescription',
-                                           'SynDynOptionDescription']
+        return False
 
     def impl_getname(self):
         return self._name
diff --git a/tiramisu/option/optiondescription.py b/tiramisu/option/optiondescription.py
index 758af28..f0f18c9 100644
--- a/tiramisu/option/optiondescription.py
+++ b/tiramisu/option/optiondescription.py
@@ -393,11 +393,12 @@ class OptionDescription(OptionDescriptionWalk):
             if child.impl_is_dynoptiondescription():
                 dynopt_names.append(name)
 
-        #better performance like this
-        valid_child = copy(child_names)
-        valid_child.sort()
+        children_ = (tuple(child_names), tuple(children))
+
+        # better performance like this
+        child_names.sort()
         old = None
-        for child in valid_child:
+        for child in child_names:
             if child == old:
                 raise ConflictError(_('duplicate option name: '
                                       '"{0}"').format(child))
@@ -407,11 +408,21 @@ class OptionDescription(OptionDescriptionWalk):
                         raise ConflictError(_('the option\'s name "{}" start as '
                                               'the dynoptiondescription\'s name "{}"').format(child, dynopt))
             old = child
-        self._children = (tuple(child_names), tuple(children))
+        self._children = children_
         self._cache_consistencies = None
         # the group_type is useful for filtering OptionDescriptions in a config
         self._group_type = groups.default
 
+    def impl_is_optiondescription(self):
+        return self.__class__.__name__ in ['OptionDescription',
+                                           'DynOptionDescription',
+                                           'SynDynOptionDescription',
+                                           'MasterSlaves']
+
+    def impl_is_dynoptiondescription(self):
+        return self.__class__.__name__ in ['DynOptionDescription',
+                                           'SynDynOptionDescription']
+
     def impl_is_master_slaves(self, *args, **kwargs):
         return False