diff --git a/tiramisu/api.py b/tiramisu/api.py
index 78857c5..f6ed3d9 100644
--- a/tiramisu/api.py
+++ b/tiramisu/api.py
@@ -156,9 +156,9 @@ class CommonTiramisuOption(CommonTiramisu):
         option = self.option_bag.option
         if not option.impl_is_optiondescription():
             if self.option_bag.index is None and option.impl_is_master_slaves('slave'):
-                raise APIError('index must be set with a slave option')
+                raise APIError(_('index must be set with the slave option "{}"').format(self.option_bag.path))
             elif self.option_bag.index is not None and not option.impl_is_master_slaves('slave'):
-                raise APIError('index must be set only with a slave option')
+                raise APIError(_('index must be set only with a slave option, not for "{}"').format(self.option_bag.path))
 
     def __getattr__(self, name):
         if not hasattr(CommonTiramisuOption, name):
@@ -350,6 +350,7 @@ class TiramisuOptionPermissive(CommonTiramisuOption):
     allow_optiondescription = True
     slave_need_index = False
 
+    # FIXME should have same api than property
     def __init__(self,
                  name: str,
                  subconfig: Union[KernelConfig, SubConfig],
@@ -533,7 +534,7 @@ class TiramisuOption(CommonTiramisu):
 
     def _find(self,
               name: str,
-              value: Union[bool, Undefined]=undefined,
+              value=undefined,
               type=None,
               first: bool=False):
         """find an option by name (only for optiondescription)"""
@@ -849,11 +850,13 @@ class TiramisuContextOption(TiramisuContext):
                   withoption=None,
                   fullpath=False):
         """return dict with path as key and value"""
-        return self.config_bag.context.make_dict(self.config_bag,
-                                                 flatten=flatten,
-                                                 fullpath=fullpath,
-                                                 withoption=withoption,
-                                                 withvalue=withvalue)
+        config_bag = self.config_bag.copy()
+        config_bag._setting_properties = self.config_bag.setting_properties - {'warnings'}
+        return config_bag.context.make_dict(config_bag,
+                                            flatten=flatten,
+                                            fullpath=fullpath,
+                                            withoption=withoption,
+                                            withvalue=withvalue)
 
     def list(self,
              type='all',
@@ -917,8 +920,8 @@ class TiramisuContextConfig(TiramisuContext):
         """find a path from option name and optionnaly a value to MetaConfig or GroupConfig"""
         if first:
             return self.config_bag.context.find_firsts(byname=name,
-                                                      byvalue=value,
-                                                      config_bag=self.config_bag)
+                                                       byvalue=value,
+                                                       config_bag=self.config_bag)
         else:
             raise APIError('not implemented yet')
 
diff --git a/tiramisu/setting.py b/tiramisu/setting.py
index 88b83f7..78fbace 100644
--- a/tiramisu/setting.py
+++ b/tiramisu/setting.py
@@ -181,7 +181,7 @@ class ConfigBag:
                 return 'validator' in self._setting_properties
             return self._validate
         if key == 'setting_properties':
-            if self.force_unrestraint:
+            if self.force_unrestraint or not self._validate:
                 return None
             return self._setting_properties
         if key == '_setting_properties':
@@ -195,10 +195,6 @@ class ConfigBag:
 
     def __setattr__(self, key, value):
         if key == 'validate':
-            try:
-                del self._setting_properties
-            except AttributeError:
-                pass
             self._validate = value
         else:
             super().__setattr__(key, value)
@@ -208,8 +204,11 @@ class ConfigBag:
         for key in self.__slots__:
             if key == 'fromconsistency' and self.fromconsistency != []:
                 kwargs['fromconsistency'] = copy(self.fromconsistency)
+            value = getattr(self, key)
+            if key == '_validate' and value == True:
+                pass
             else:
-                kwargs[key] = getattr(self, key)
+                kwargs[key] = value
         return ConfigBag(**kwargs)