diff --git a/tiramisu/option.py b/tiramisu/option.py
index 3c0ede1..c3caae3 100644
--- a/tiramisu/option.py
+++ b/tiramisu/option.py
@@ -27,7 +27,7 @@ from IPy import IP
 import warnings
 
 from tiramisu.error import ConfigError, ConflictError, ValueWarning
-from tiramisu.setting import groups, multitypes
+from tiramisu.setting import groups, multitypes, log
 from tiramisu.i18n import _
 from tiramisu.autolib import carry_out_calculation
 
@@ -430,10 +430,14 @@ class Option(BaseOption):
                 val_validator(_value)
                 self._second_level_validation(_value, self._warnings_only)
             except ValueError as error:
+                log.debug(_('do_validation for {0}: error in value').format(
+                    self._name), exc_info=True)
                 if self._warnings_only:
                     warning = error
                     error = None
             except ValueWarning as warning:
+                log.debug(_('do_validation for {0}: warning in value').format(
+                    self._name), exc_info=True)
                 pass
             if error is None and warning is None:
                 try:
@@ -441,8 +445,12 @@ class Option(BaseOption):
                     if context is not None:
                         descr._valid_consistency(self, _value, context, _index)
                 except ValueError as error:
+                    log.debug(_('do_validation for {0}: error in consistency').format(
+                        self._name), exc_info=True)
                     pass
                 except ValueWarning as warning:
+                    log.debug(_('do_validation for {0}: warning in consistency').format(
+                        self._name), exc_info=True)
                     pass
             if warning:
                 msg = _("warning on the value of the option {0}: {1}").format(
@@ -1543,10 +1551,10 @@ def validate_callback(callback, callback_params, type_):
                         if not isinstance(option, Option) and not \
                                 isinstance(option, SymLinkOption):
                             raise ValueError(_('{0}_params must have an option'
-                                            ' not a {0} for first argument'
-                                            ).format(type_, type(option)))
+                                               ' not a {0} for first argument'
+                                               ).format(type_, type(option)))
                         if force_permissive not in [True, False]:
                             raise ValueError(_('{0}_params must have a boolean'
-                                            ' not a {0} for second argument'
-                                            ).format(type_, type(
-                                                force_permissive)))
+                                               ' not a {0} for second argument'
+                                               ).format(type_, type(
+                                                   force_permissive)))
diff --git a/tiramisu/setting.py b/tiramisu/setting.py
index a945a2c..d7925fa 100644
--- a/tiramisu/setting.py
+++ b/tiramisu/setting.py
@@ -17,6 +17,7 @@
 # ____________________________________________________________
 from time import time
 from copy import copy
+from logging import getLogger
 import weakref
 from tiramisu.error import (RequirementError, PropertiesOptionError,
                             ConstError, ConfigError)
@@ -99,6 +100,9 @@ rw_append = set(['frozen', 'disabled', 'validator', 'hidden'])
 rw_remove = set(['permissive', 'everything_frozen', 'mandatory'])
 
 
+log = getLogger('tiramisu')
+
+
 # ____________________________________________________________
 class _NameSpace(object):
     """convenient class that emulates a module