diff --git a/test/test_config.py b/test/test_config.py
index ebfbc61..f660cf5 100644
--- a/test/test_config.py
+++ b/test/test_config.py
@@ -131,8 +131,10 @@ def test_cfgimpl_get_home_by_path():
     config.bool = False
     assert config.cfgimpl_get_home_by_path('gc.dummy')[1] == 'dummy'
     assert config.cfgimpl_get_home_by_path('dummy')[1] == 'dummy'
-    #assert config.getpaths(include_groups=False) == ['gc.name', 'gc.dummy', 'gc.float', 'bool', 'objspace', 'wantref', 'str', 'wantframework', 'int', 'boolop']
-    #assert config.getpaths(include_groups=True) == ['gc', 'gc.name', 'gc.dummy', 'gc.float', 'bool', 'objspace', 'wantref', 'str', 'wantframework', 'int', 'boolop']
+
+
+def test_not_valid_properties():
+    raises(TypeError, "stroption = StrOption('str', 'Test string option', default='abc', properties=['mandatory',])")
 
 
 def test_information_config():
@@ -142,6 +144,7 @@ def test_information_config():
     config.impl_set_information('info', string)
     assert config.impl_get_information('info') == string
     raises(ValueError, "config.impl_get_information('noinfo')")
+    assert config.impl_get_information('noinfo', 'default') == 'default'
 
 
 #FIXME test impl_get_xxx pour OD ou ne pas cacher
@@ -150,8 +153,10 @@ def test_config_impl_get_path_by_opt():
     config = Config(descr)
     dummy = config.unwrap_from_path('gc.dummy')
     boo = config.unwrap_from_path('bool')
+    unknown = IntOption('test', '')
     assert config.cfgimpl_get_description().impl_get_path_by_opt(boo) == 'bool'
     assert config.cfgimpl_get_description().impl_get_path_by_opt(dummy) == 'gc.dummy'
+    raises(AttributeError, "config.cfgimpl_get_description().impl_get_path_by_opt(unknown)")
 
 
 def test_config_impl_get_opt_by_path():
@@ -161,6 +166,7 @@ def test_config_impl_get_opt_by_path():
     boo = config.unwrap_from_path('bool')
     assert config.cfgimpl_get_description().impl_get_opt_by_path('bool') == boo
     assert config.cfgimpl_get_description().impl_get_opt_by_path('gc.dummy') == dummy
+    raises(AttributeError, "config.cfgimpl_get_description().impl_get_opt_by_path('gc.unknown')")
 
 
 def test_information_display():
@@ -235,7 +241,40 @@ def test_duplicated_option_diff_od():
     raises(ConflictError, "d2 = OptionDescription('od2', '', [g1])")
 
 
+
 def test_cannot_assign_value_to_option_description():
     descr = make_description()
     cfg = Config(descr)
     raises(TypeError, "cfg.gc = 3")
+
+
+def test_config_multi():
+    i1 = IntOption('test1', '', multi=True)
+    i2 = IntOption('test2', '', multi=True, default_multi=1)
+    i3 = IntOption('test3', '', default=[2], multi=True, default_multi=1)
+    od = OptionDescription('test', '', [i1, i2, i3])
+    config = Config(od)
+    assert config.test1 == []
+    assert config.test2 == []
+    config.test2.append()
+    assert config.test2 == [1]
+    assert config.test3 == [2]
+    config.test3.append()
+    assert config.test3 == [2, 1]
+
+
+def test_no_validation():
+    i1 = IntOption('test1', '')
+    od = OptionDescription('test', '', [i1])
+    c = Config(od)
+    setting = c.cfgimpl_get_settings()
+    c.test1 = 1
+    raises(ValueError, 'c.test1 = "yes"')
+    assert c.test1 == 1
+    setting.remove('validator')
+    c.test1 = "yes"
+    assert c.test1 == "yes"
+    setting.append('validator')
+    raises(ValueError, 'c.test1')
+    del(c.test1)
+    assert c.test1 == None
diff --git a/test/test_config_ip.py b/test/test_config_ip.py
index b7d3010..581cbd2 100644
--- a/test/test_config_ip.py
+++ b/test/test_config_ip.py
@@ -21,6 +21,11 @@ def test_ip():
     c.b = '0.0.0.0'
     raises(ValueError, "c.b = '255.255.255.0'")
 
+    raises(ValueError, "IPOption('a', 'ip', default='192.000.023.01')")
+    d = IPOption('a', 'ip', default='192.0.23.1')
+    od = OptionDescription('od', '', [d])
+    c = Config(od)
+    raises(ValueError, "c.a = '192.000.023.01'")
 
 def test_ip_default():
     a = IPOption('a', '', '88.88.88.88')
diff --git a/test/test_option.py b/test/test_option.py
index 0492ed2..ec769c5 100644
--- a/test/test_option.py
+++ b/test/test_option.py
@@ -2,8 +2,13 @@
 and to compare them
 """
 import autopath
+from py.test import raises
 
-from tiramisu.option import BoolOption, IntOption
+from tiramisu.option import IntOption, OptionDescription
+
+
+def a_func():
+    return None
 
 
 #def test_option_comparison():
@@ -36,3 +41,60 @@ from tiramisu.option import BoolOption, IntOption
 #    assert dummy1 != dummy5
 #    assert dummy1 == dummy6
 #    assert dummy1 != dummy7
+
+
+def test_option_valid_name():
+    IntOption('test', '')
+    raises(ValueError, 'IntOption(1, "")')
+    raises(ValueError, 'IntOption("impl_test", "")')
+    raises(ValueError, 'IntOption("_test", "")')
+    raises(ValueError, 'IntOption("unwrap_from_path", "")')
+
+
+def test_option_with_callback():
+    #no default value with callback
+    raises(ValueError, "IntOption('test', '', default=1, callback=a_func)")
+
+
+def test_option_get_information():
+    description = "it's ok"
+    string = 'some informations'
+    i = IntOption('test', description)
+    i.impl_set_information('info', string)
+    assert i.impl_get_information('info') == string
+    raises(ValueError, "i.impl_get_information('noinfo')")
+    assert i.impl_get_information('noinfo', 'default') == 'default'
+    assert i.impl_get_information('doc') == description
+    assert i.impl_getdoc() == description
+
+
+def test_optiondescription_get_information():
+    description = "it's ok"
+    string = 'some informations'
+    o = OptionDescription('test', description, [])
+    o.impl_set_information('info', string)
+    assert o.impl_get_information('info') == string
+    raises(ValueError, "o.impl_get_information('noinfo')")
+    assert o.impl_get_information('noinfo', 'default') == 'default'
+    assert o.impl_get_information('doc') == description
+    assert o.impl_getdoc() == description
+
+
+def test_option_multi():
+    IntOption('test', '', multi=True)
+    IntOption('test', '', multi=True, default_multi=1)
+    IntOption('test', '', default=[1], multi=True, default_multi=1)
+    #add default_multi to not multi's option
+    raises(ValueError, "IntOption('test', '', default_multi=1)")
+    #unvalid default_multi
+    raises(ValueError, "IntOption('test', '', multi=True, default_multi='yes')")
+    #not default_multi with callback
+    raises(ValueError, "IntOption('test', '', multi=True, default_multi=1, callback=a_func)")
+
+
+def test_option_is_multi_by_default():
+    assert IntOption('test', '').impl_is_empty_by_default() is True
+    assert IntOption('test', '', 1).impl_is_empty_by_default() is False
+    assert IntOption('test', '', multi=True).impl_is_empty_by_default() is True
+    assert IntOption('test', '', [1], multi=True).impl_is_empty_by_default() is False
+    assert IntOption('test', '', multi=True, default_multi=1).impl_is_empty_by_default() is True
diff --git a/test/test_option_calculation.py b/test/test_option_calculation.py
index a1a9fd1..2cacf5e 100644
--- a/test/test_option_calculation.py
+++ b/test/test_option_calculation.py
@@ -21,7 +21,13 @@ def return_list(value=None):
 
 
 def return_list2(*args):
-    return list(args)
+    l = []
+    for arg in args:
+        if isinstance(arg, list):
+            l.extend(arg)
+        else:
+            l.append(arg)
+    return l
 
 
 def return_value(value=None):
@@ -34,6 +40,10 @@ def return_value2(*args, **kwargs):
     return value
 
 
+def return_calc(i, j, k):
+    return i + j + k
+
+
 def make_description():
     gcoption = ChoiceOption('name', 'GC name', ('ref', 'framework'), 'ref')
     gcdummy = BoolOption('dummy', 'dummy', default=False)
@@ -93,83 +103,6 @@ def test_identical_paths():
     raises(ConflictError, "make_description_duplicates()")
 
 
-def make_description2():
-    gcoption = ChoiceOption('name', 'GC name', ['ref', 'framework'], 'ref')
-    gcdummy = BoolOption('dummy', 'dummy', default=False)
-
-    floatoption = FloatOption('float', 'Test float option', default=2.3)
-
-    objspaceoption = ChoiceOption('objspace', 'Object space',
-                                  ['std', 'thunk'], 'std')
-    booloption = BoolOption('bool', 'Test boolean option', default=True)
-    intoption = IntOption('int', 'Test int option', default=0)
-    stroption = StrOption('str', 'Test string option', default="abc")
-    # first multi
-    boolop = BoolOption('boolop', 'Test boolean option op', default=True)
-    boolop.enable_multi()
-    wantref_option = BoolOption('wantref', 'Test requires', default=False,
-                                requires=({'option': boolop, 'expected': True, 'action': 'hidden'},))
-    # second multi
-    wantframework_option = BoolOption('wantframework', 'Test requires',
-                                      default=False,
-                                      requires=({'option': boolop, 'expected': True, 'action': 'hidden'},))
-    wantframework_option.enable_multi()
-
-    gcgroup = OptionDescription('gc', '', [gcoption, gcdummy, floatoption])
-    descr = OptionDescription('constraints', '', [gcgroup, booloption, objspaceoption,
-                              wantref_option, stroption,
-                              wantframework_option,
-                              intoption, boolop])
-    return descr
-
-
-# FIXME: il faudra tester les validations sur les multis
-#def test_multi_constraints():
-#    "a multi in a constraint has to have the same length"
-#    descr = make_description2()
-#    cfg = Config(descr)
-#    cfg.boolop = [True, True, False]
-#    cfg.wantframework = [False, False, True]
-#
-#def test_multi_raise():
-#    "a multi in a constraint has to have the same length"
-#    # FIXME fusionner les deux tests, MAIS PROBLEME :
-#    # il ne devrait pas etre necessaire de refaire une config
-#    # si la valeur est modifiee une deuxieme fois ->
-#    #raises(ConflictConfigError, "cfg.wantframework = [False, False, True]")
-#    #   ExceptionFailure: 'DID NOT RAISE'
-#    descr = make_description2()
-#    cfg = Config(descr)
-#    cfg.boolop = [True]
-#    raises(ConflictConfigError, "cfg.wantframework = [False, False, True]")
-# ____________________________________________________________
-# adding dynamically new options description schema
-#def test_newoption_add_in_descr():
-#    descr = make_description()
-#    newoption = BoolOption('newoption', 'dummy twoo', default=False)
-#    descr.add_child(newoption)
-#    config = Config(descr)
-#    assert config.newoption == False
-
-#def test_newoption_add_in_subdescr():
-#    descr = make_description()
-#    newoption = BoolOption('newoption', 'dummy twoo', default=False)
-#    descr.gc.add_child(newoption)
-#    config = Config(descr)
-#    config.bool = False
-#    assert config.gc.newoption == False
-
-#def test_newoption_add_in_config():
-#    descr = make_description()
-#    config = Config(descr)
-#    config.bool = False
-#    newoption = BoolOption('newoption', 'dummy twoo', default=False)
-#    descr.add_child(newoption)
-#    config.cfgimpl_update()
-#    assert config.newoption == False
-# ____________________________________________________________
-
-
 def make_description_requires():
     gcoption = ChoiceOption('name', 'GC name', ('ref', 'framework'), 'ref')
     gcdummy = BoolOption('dummy', 'dummy', default=False)
@@ -310,6 +243,19 @@ def test_callback():
     assert cfg.val1 == 'val'
 
 
+def test_callback_params_without_callback():
+    raises(ValueError, "StrOption('val2', '', callback_params={'': ('yes',)})")
+
+
+def test_callback_invalid():
+    raises(ValueError, 'val1 = StrOption("val1", "", callback="string")')
+    raises(ValueError, 'val1 = StrOption("val1", "", callback=return_val, callback_params="string")')
+    val1 = StrOption('val1', "", 'val')
+    raises(ValueError, "StrOption('val2', '', callback=return_value, callback_params={'': 'string'})")
+    raises(ValueError, "StrOption('val4', '', callback=return_value, callback_params={'value': (('string', False),)})")
+    raises(ValueError, "StrOption('val4', '', callback=return_value, callback_params={'value': ((val1, 'string'),)})")
+
+
 def test_callback_value():
     val1 = StrOption('val1', "", 'val')
     val2 = StrOption('val2', "", callback=return_value, callback_params={'': ((val1, False),)})
@@ -422,7 +368,7 @@ def test_callback_multi_value():
     cfg.val1.append('new-val2')
     assert cfg.val1 == ['new-val', 'new-val2']
     assert cfg.val2 == ['new-val', 'new-val2']
-    assert cfg.val4 == ['new-val', 'yes', 'new-val2', 'yes']
+    assert cfg.val4 == ['new-val', 'new-val2', 'yes']
     del(cfg.val1)
     assert cfg.val1 == ['val']
     assert cfg.val2 == ['val']
@@ -444,6 +390,14 @@ def test_callback_multi_list():
     assert cfg.val1 == ['val', 'val']
 
 
+def test_callback_multi_list_extend():
+    val1 = StrOption('val1', "", callback=return_list2, callback_params={'': (['1', '2', '3'], ['4', '5'])}, multi=True)
+    maconfig = OptionDescription('rootconfig', '', [val1])
+    cfg = Config(maconfig)
+    cfg.read_write()
+    assert cfg.val1 == ['1', '2', '3', '4', '5']
+
+
 def test_callback_master_and_slaves_master():
     val1 = StrOption('val1', "", multi=True, callback=return_val)
     val2 = StrOption('val2', "", multi=True)
@@ -453,7 +407,7 @@ def test_callback_master_and_slaves_master():
     cfg = Config(maconfig)
     cfg.read_write()
     assert cfg.val1.val1 == ['val']
-    cfg.val1.val1.append(None)
+    cfg.val1.val1.append()
     assert cfg.val1.val1 == ['val', 'val']
     assert cfg.val1.val2 == [None, None]
 
@@ -468,7 +422,7 @@ def test_callback_master_and_slaves_master_list():
     cfg.read_write()
     assert cfg.val1.val1 == ['val', 'val']
     assert cfg.val1.val2 == [None, None]
-    cfg.val1.val1.append(None)
+    cfg.val1.val1.append()
     assert cfg.val1.val1 == ['val', 'val', None]
     assert cfg.val1.val2 == [None, None, None]
     del(cfg.val1.val1)
@@ -536,7 +490,8 @@ def test_callback_master_and_slaves_value():
     val3 = StrOption('val3', "", multi=True, callback=return_value, callback_params={'': ('yes',)})
     val4 = StrOption('val4', '', multi=True, default=['val10', 'val11'])
     val5 = StrOption('val5', "", multi=True, callback=return_value, callback_params={'': ((val4, False),)})
-    interface1 = OptionDescription('val1', '', [val1, val2, val3, val5])
+    val6 = StrOption('val6', "", multi=True, callback=return_value, callback_params={'': ((val5, False),)})
+    interface1 = OptionDescription('val1', '', [val1, val2, val3, val5, val6])
     interface1.impl_set_group_type(groups.master)
     maconfig = OptionDescription('rootconfig', '', [interface1, val4])
     cfg = Config(maconfig)
@@ -545,30 +500,35 @@ def test_callback_master_and_slaves_value():
     assert cfg.val1.val2 == []
     assert cfg.val1.val3 == []
     assert cfg.val1.val5 == []
+    assert cfg.val1.val6 == []
     #
     cfg.val1.val1 = ['val1']
     assert cfg.val1.val1 == ['val1']
     assert cfg.val1.val2 == ['val1']
     assert cfg.val1.val3 == ['yes']
     assert cfg.val1.val5 == ['val10']
+    assert cfg.val1.val6 == ['val10']
     #
     cfg.val1.val1.append('val2')
     assert cfg.val1.val1 == ['val1', 'val2']
     assert cfg.val1.val2 == ['val1', 'val2']
     assert cfg.val1.val3 == ['yes', 'yes']
     assert cfg.val1.val5 == ['val10', 'val11']
+    assert cfg.val1.val6 == ['val10', 'val11']
     #
     cfg.val1.val1 = ['val1', 'val2', 'val3']
     assert cfg.val1.val1 == ['val1', 'val2', 'val3']
     assert cfg.val1.val2 == ['val1', 'val2', 'val3']
     assert cfg.val1.val3 == ['yes', 'yes', 'yes']
     assert cfg.val1.val5 == ['val10', 'val11', None]
+    assert cfg.val1.val6 == ['val10', 'val11', None]
     #
     cfg.val1.val1.pop(2)
     assert cfg.val1.val1 == ['val1', 'val2']
     assert cfg.val1.val2 == ['val1', 'val2']
     assert cfg.val1.val3 == ['yes', 'yes']
     assert cfg.val1.val5 == ['val10', 'val11']
+    assert cfg.val1.val6 == ['val10', 'val11']
     #
     cfg.val1.val2 = ['val2', 'val2']
     cfg.val1.val3 = ['val2', 'val2']
@@ -576,11 +536,13 @@ def test_callback_master_and_slaves_value():
     assert cfg.val1.val2 == ['val2', 'val2']
     assert cfg.val1.val3 == ['val2', 'val2']
     assert cfg.val1.val5 == ['val2', 'val2']
+    assert cfg.val1.val6 == ['val2', 'val2']
     #
     cfg.val1.val1.append('val3')
     assert cfg.val1.val2 == ['val2', 'val2', 'val3']
     assert cfg.val1.val3 == ['val2', 'val2', 'yes']
     assert cfg.val1.val5 == ['val2', 'val2', None]
+    assert cfg.val1.val6 == ['val2', 'val2', None]
     cfg.cfgimpl_get_settings().remove('cache')
     cfg.val4 = ['val10', 'val11', 'val12']
     #if value is already set, not updated !
@@ -588,6 +550,69 @@ def test_callback_master_and_slaves_value():
     cfg.val1.val1.append('val3')
     cfg.val1.val1 = ['val1', 'val2', 'val3']
     assert cfg.val1.val5 == ['val2', 'val2', 'val12']
+    assert cfg.val1.val6 == ['val2', 'val2', 'val12']
+
+
+def test_callback_master():
+    val2 = StrOption('val2', "", multi=True, callback=return_value)
+    val1 = StrOption('val1', "", multi=True, callback=return_value, callback_params={'': ((val2, False),)})
+    interface1 = OptionDescription('val1', '', [val1, val2])
+    raises(ValueError, "interface1.impl_set_group_type(groups.master)")
+
+
+def test_callback_master_and_other_master_slave():
+    val1 = StrOption('val1', "", multi=True)
+    val2 = StrOption('val2', "", multi=True)
+    val3 = StrOption('val3', "", multi=True)
+    val4 = StrOption('val4', '', multi=True, default=['val10', 'val11'])
+    val5 = StrOption('val5', "", multi=True, callback=return_value, callback_params={'': ((val1, False),)})
+    val6 = StrOption('val6', "", multi=True, callback=return_value, callback_params={'': ((val2, False),)})
+    interface1 = OptionDescription('val1', '', [val1, val2, val3])
+    interface1.impl_set_group_type(groups.master)
+    interface2 = OptionDescription('val4', '', [val4, val5, val6])
+    interface2.impl_set_group_type(groups.master)
+    maconfig = OptionDescription('rootconfig', '', [interface1, interface2])
+    cfg = Config(maconfig)
+    cfg.read_write()
+    assert cfg.val4.val4 == ['val10', 'val11']
+    assert cfg.val4.val5 == [None, None]
+    assert cfg.val4.val6 == [None, None]
+    cfg.val1.val1 = ['yes']
+    assert cfg.val4.val4 == ['val10', 'val11']
+    assert cfg.val4.val5 == ['yes', None]
+    assert cfg.val4.val6 == [None, None]
+    cfg.val1.val2 = ['no']
+    assert cfg.val4.val4 == ['val10', 'val11']
+    assert cfg.val4.val5 == ['yes', None]
+    assert cfg.val4.val6 == ['no', None]
+    cfg.val1.val1 = ['yes', 'yes', 'yes']
+    cfg.val1.val2 = ['no', 'no', 'no']
+    assert cfg.val4.val4 == ['val10', 'val11']
+    assert cfg.val4.val5 == ['yes', 'yes']
+    assert cfg.val4.val6 == ['no', 'no']
+
+
+def test_callback_different_type():
+    val = IntOption('val', "", default=2)
+    val_ = IntOption('val_', "", default=3)
+    val1 = IntOption('val1', "", multi=True)
+    val2 = IntOption('val2', "", multi=True, callback=return_calc, callback_params={'': ((val, False), (val1, False)), 'k': ((val_, False),)})
+    interface1 = OptionDescription('val1', '', [val1, val2])
+    interface1.impl_set_group_type(groups.master)
+    maconfig = OptionDescription('rootconfig', '', [interface1, val, val_])
+    cfg = Config(maconfig)
+    cfg.read_write()
+    assert cfg.val1.val1 == []
+    assert cfg.val1.val2 == []
+    cfg.val1.val1 = [1]
+    assert cfg.val1.val1 == [1]
+    assert cfg.val1.val2 == [6]
+    cfg.val1.val1 = [1, 3]
+    assert cfg.val1.val1 == [1, 3]
+    assert cfg.val1.val2 == [6, 8]
+    cfg.val1.val1 = [1, 3, 5]
+    assert cfg.val1.val1 == [1, 3, 5]
+    assert cfg.val1.val2 == [6, 8, 10]
 
 
 def test_callback_hidden():
@@ -654,7 +679,7 @@ def test_callback_multi_list_params():
     maconfig = OptionDescription('rootconfig', '', [val1, oval2])
     cfg = Config(maconfig)
     cfg.read_write()
-    assert cfg.val2.val2 == ['val', 'val', 'val', 'val']
+    assert cfg.val2.val2 == ['val', 'val']
 
 
 def test_callback_multi_list_params_key():
@@ -664,31 +689,4 @@ def test_callback_multi_list_params_key():
     maconfig = OptionDescription('rootconfig', '', [val1, oval2])
     cfg = Config(maconfig)
     cfg.read_write()
-    assert cfg.val2.val2 == ['val', 'val', 'val', 'val']
-
-
-def test_callback_multi_multi():
-    val1 = StrOption('val1', "", multi=True, default=['val1', 'val2', 'val3'])
-    val2 = StrOption('val2', "", multi=True, default=['val11', 'val12'])
-    val3 = StrOption('val3', "", default='val4')
-    val4 = StrOption('val4', "", multi=True, callback=return_list2, callback_params={'': ((val1, False), (val2, False))})
-    val5 = StrOption('val5', "", multi=True, callback=return_list2, callback_params={'': ((val1, False), (val3, False))})
-    val6 = StrOption('val6', "", multi=True, default=['val21', 'val22', 'val23'])
-    val7 = StrOption('val7', "", multi=True, callback=return_list2, callback_params={'': ((val1, False), (val6, False))})
-    raises(ValueError, "StrOption('val8', '', multi=True, callback=return_list2, callback_params={'value': ((val1, False), (val6, False))})")
-    maconfig = OptionDescription('rootconfig', '', [val1, val2, val3, val4, val5, val6, val7])
-    cfg = Config(maconfig)
-    cfg.read_write()
-    raises(ConfigError, "cfg.val4")
-    assert cfg.val5 == ['val1', 'val4', 'val2', 'val4', 'val3', 'val4']
-    assert cfg.val7 == ['val1', 'val21', 'val2', 'val22', 'val3', 'val23']
-
-
-def test_multi_with_no_value():
-    #First option return [] (so without value)
-    val1 = StrOption('val1', "", ['val'], multi=True)
-    val2 = StrOption('val2', "", multi=True)
-    val3 = StrOption('val3', '', multi=True, callback=return_value, callback_params={'': ((val2, False),), 'value': ((val1, False),)})
-    od = OptionDescription('od', '', [val1, val2, val3])
-    c = Config(od)
-    raises(ConfigError, "c.val3")
+    assert cfg.val2.val2 == ['val', 'val']
diff --git a/test/test_option_consistency.py b/test/test_option_consistency.py
index 075f259..5e85530 100644
--- a/test/test_option_consistency.py
+++ b/test/test_option_consistency.py
@@ -8,6 +8,17 @@ from tiramisu.option import IPOption, NetworkOption, NetmaskOption, IntOption,\
 from tiramisu.error import ConfigError
 
 
+def test_consistency():
+    a = IntOption('a', '')
+    b = IntOption('b', '')
+    od = OptionDescription('od', '', [a, b])
+    a.impl_add_consistency('not_equal', b)
+    #consistency to itself
+    raises(ConfigError, "a.impl_add_consistency('not_equal', a)")
+    #consistency with string
+    raises(ConfigError, "a.impl_add_consistency('not_equal', 'a')")
+
+
 def test_consistency_not_equal():
     a = IntOption('a', '')
     b = IntOption('b', '')
diff --git a/test/test_option_owner.py b/test/test_option_owner.py
index bc96285..b758e91 100644
--- a/test/test_option_owner.py
+++ b/test/test_option_owner.py
@@ -5,7 +5,7 @@ from tiramisu.setting import owners
 from tiramisu.config import Config
 from tiramisu.option import ChoiceOption, BoolOption, IntOption, FloatOption, \
     StrOption, OptionDescription
-from tiramisu.error import ConfigError
+from tiramisu.error import ConfigError, ConstError
 
 
 def make_description():
@@ -52,6 +52,17 @@ def test_addowner():
     assert cfg.getowner(gcdummy) == owners.gen_config
 
 
+def test_addowner_multiple_time():
+    owners.addowner("testowner")
+    raises(ConstError, 'owners.addowner("testowner")')
+
+
+def test_delete_owner():
+    owners.addowner('deleted')
+    raises(ConstError, 'del(owners.deleted)')
+    raises(ValueError, 'del(owners.deleted2)')
+
+
 def test_owner_is_not_a_string():
     gcdummy = BoolOption('dummy', 'dummy', default=False)
     descr = OptionDescription('tiramisu', '', [gcdummy])
diff --git a/test/test_permissive.py b/test/test_permissive.py
index 38a8bcf..20e6535 100644
--- a/test/test_permissive.py
+++ b/test/test_permissive.py
@@ -9,7 +9,8 @@ from tiramisu.error import PropertiesOptionError
 
 def make_description():
     u1 = IntOption('u1', '', properties=('frozen', 'mandatory', 'disabled', ))
-    return OptionDescription('od1', '', [u1])
+    u2 = IntOption('u2', '', properties=('frozen', 'mandatory', 'disabled', ))
+    return OptionDescription('od1', '', [u1, u2])
 
 
 def test_permissive():
@@ -91,3 +92,116 @@ def test_invalid_permissive():
     setting = config.cfgimpl_get_settings()
     config.read_write()
     raises(TypeError, "setting.setpermissive(['frozen', 'disabled',])")
+
+
+def test_permissive_option():
+    descr = make_description()
+    u1 = descr.u1
+    config = Config(descr)
+    setting = config.cfgimpl_get_settings()
+    config.read_write()
+
+    props = []
+    try:
+        config.u1
+    except PropertiesOptionError as err:
+        props = err.proptype
+    assert props == ['disabled']
+    props = []
+    try:
+        config.u2
+    except PropertiesOptionError as err:
+        props = err.proptype
+    assert props == ['disabled']
+
+    setting.setpermissive(('disabled',), u1)
+    props = []
+    try:
+        config.u1
+    except PropertiesOptionError as err:
+        props = err.proptype
+    assert props == ['disabled']
+    props = []
+    try:
+        config.u2
+    except PropertiesOptionError as err:
+        props = err.proptype
+    assert props == ['disabled']
+
+    setting.append('permissive')
+    config.u1
+    props = []
+    try:
+        config.u2
+    except PropertiesOptionError as err:
+        props = err.proptype
+    assert props == ['disabled']
+
+    setting.remove('permissive')
+    props = []
+    try:
+        config.u1
+    except PropertiesOptionError as err:
+        props = err.proptype
+    assert props == ['disabled']
+    props = []
+    try:
+        config.u2
+    except PropertiesOptionError as err:
+        props = err.proptype
+    assert props == ['disabled']
+
+
+def test_permissive_option_mandatory():
+    descr = make_description()
+    u1 = descr.u1
+    config = Config(descr)
+    setting = config.cfgimpl_get_settings()
+    config.read_only()
+    props = []
+    try:
+        config.u1
+    except PropertiesOptionError as err:
+        props = err.proptype
+    assert set(props) == set(['disabled', 'mandatory'])
+    setting.setpermissive(('mandatory', 'disabled',), u1)
+    setting.append('permissive')
+    config.u1
+    setting.remove('permissive')
+    try:
+        config.u1
+    except PropertiesOptionError as err:
+        props = err.proptype
+    assert set(props) == set(['disabled', 'mandatory'])
+
+
+def test_permissive_option_frozen():
+    descr = make_description()
+    config = Config(descr)
+    u1 = descr.u1
+    setting = config.cfgimpl_get_settings()
+    config.read_write()
+    setting.setpermissive(('frozen', 'disabled'), u1)
+    try:
+        config.u1 = 1
+    except PropertiesOptionError as err:
+        props = err.proptype
+    assert set(props) == set(['frozen', 'disabled'])
+    setting.append('permissive')
+    config.u1 = 1
+    assert config.u1 == 1
+    setting.remove('permissive')
+    try:
+        config.u1 = 1
+    except PropertiesOptionError as err:
+        props = err.proptype
+    assert set(props) == set(['frozen', 'disabled'])
+
+
+def test_invalid_option_permissive():
+    descr = make_description()
+    u1 = descr.u1
+    config = Config(descr)
+    setting = config.cfgimpl_get_settings()
+    config.read_write()
+    raises(TypeError, "setting.setpermissive(['frozen', 'disabled',], u1)")
diff --git a/test/test_requires.py b/test/test_requires.py
index 69501b9..4f35cfd 100644
--- a/test/test_requires.py
+++ b/test/test_requires.py
@@ -26,6 +26,20 @@ def test_requires():
     assert props == ['disabled']
 
 
+def test_requires_invalid():
+    a = BoolOption('activate_service', '', True)
+    raises(ValueError, "IPOption('ip_address_service', '', requires='string')")
+    raises(ValueError, "IPOption('ip_address_service', '', requires=[{'option': a, 'expected': False, 'action': 'disabled', 'unknown': True}])")
+    raises(ValueError, "IPOption('ip_address_service', '', requires=[{'option': a, 'expected': False}])")
+    raises(ValueError, "IPOption('ip_address_service', '', requires=[{'option': a, 'action': 'disabled'}])")
+    raises(ValueError, "IPOption('ip_address_service', '', requires=[{'expected': False, 'action': 'disabled'}])")
+    raises(ValueError, "IPOption('ip_address_service', '', requires=[{'option': a, 'expected': False, 'action': 'disabled', 'inverse': 'string'}])")
+    raises(ValueError, "IPOption('ip_address_service', '', requires=[{'option': a, 'expected': False, 'action': 'disabled', 'transitive': 'string'}])")
+    raises(ValueError, "IPOption('ip_address_service', '', requires=[{'option': a, 'expected': False, 'action': 'disabled', 'same_action': 'string'}])")
+    raises(ValueError, "IPOption('ip_address_service', '', requires=[{'option': 'string', 'expected': False, 'action': 'disabled'}])")
+    raises(ValueError, "IPOption('ip_address_service', '', requires=[{'option': a, 'expected': 'string', 'action': 'disabled'}])")
+
+
 def test_requires_same_action():
     a = BoolOption('activate_service', '', True)
     b = BoolOption('activate_service_web', '', True,
@@ -504,6 +518,11 @@ def test_requires_multi_disabled_inverse_2():
 #    c.cfgimpl_get_settings()[b].append("test")
 
 
+def test_requires_different_inverse():
+    a = BoolOption('activate_service', '', True)
+    raises(ValueError, "IPOption('ip_address_service', '', requires=[{'option': a, 'expected': True, 'action': 'disabled', 'inverse': True}, {'option': a, 'expected': True, 'action': 'disabled', 'inverse': False}])")
+
+
 def test_requires_recursive_path():
     a = BoolOption('activate_service', '', True)
     b = IPOption('ip_address_service', '',
diff --git a/tiramisu/autolib.py b/tiramisu/autolib.py
index eea1c62..2c6c7d8 100644
--- a/tiramisu/autolib.py
+++ b/tiramisu/autolib.py
@@ -20,15 +20,17 @@
 # ____________________________________________________________
 "enables us to carry out a calculation and return an option's value"
 from tiramisu.error import PropertiesOptionError, ConfigError
+from tiramisu.setting import multitypes
 from tiramisu.i18n import _
 # ____________________________________________________________
 
 
-def carry_out_calculation(name, config, callback, callback_params,
+def carry_out_calculation(option, config, callback, callback_params,
                           index=None, max_len=None):
     """a function that carries out a calculation for an option's value
 
     :param name: the option name (`opt.impl_getname()`)
+    :param name: the option
     :param config: the context config in order to have
                    the whole options available
     :param callback: the name of the callback function
@@ -49,13 +51,13 @@ def carry_out_calculation(name, config, callback, callback_params,
     Values could have multiple values only when key is ''.
 
     * if no callback_params:
-      => calculate()
+      => calculate(<function func at 0x2092320>, [], {})
 
     * if callback_params={'': ('yes',)}
-      => calculate('yes')
+      => calculate(<function func at 0x2092320>, ['yes'], {})
 
     * if callback_params={'value': ('yes',)}
-      => calculate(value='yes')
+      => calculate(<function func at 0x165b320>, [], {'value': 'yes'})
 
     * if callback_params={'': ('yes', 'no')}
       => calculate('yes', 'no')
@@ -63,58 +65,71 @@ def carry_out_calculation(name, config, callback, callback_params,
     * if callback_params={'value': ('yes', 'no')}
       => ValueError()
 
+    * if callback_params={'': (['yes', 'no'],)}
+      => calculate(<function func at 0x176b320>, ['yes', 'no'], {})
+
+    * if callback_params={'value': ('yes', 'no')}
+      => raises ValueError()
+
     * if callback_params={'': ((opt1, False),)}
 
        - a simple option:
          opt1 == 11
-         => calculate(11)
+         => calculate(<function func at 0x1cea320>, [11], {})
 
-       - a multi option:
+       - a multi option and not master/slave:
          opt1 == [1, 2, 3]
-         => calculate(1)
-         => calculate(2)
-         => calculate(3)
+         => calculate(<function func at 0x223c320>, [[1, 2, 3]], {})
+
+       - option is master or slave of opt1:
+         opt1 == [1, 2, 3]
+         => calculate(<function func at 0x223c320>, [1], {})
+         => calculate(<function func at 0x223c320>, [2], {})
+         => calculate(<function func at 0x223c320>, [3], {})
+
+      - opt is a master or slave but not related to option:
+        opt1 == [1, 2, 3]
+        => calculate(<function func at 0x11b0320>, [[1, 2, 3]], {})
 
     * if callback_params={'value': ((opt1, False),)}
 
        - a simple option:
          opt1 == 11
-         => calculate(value=11)
+         => calculate(<function func at 0x17ff320>, [], {'value': 11})
 
        - a multi option:
          opt1 == [1, 2, 3]
-         => calculate(value=1)
-         => calculate(value=2)
-         => calculate(value=3)
+         => calculate(<function func at 0x1262320>, [], {'value': [1, 2, 3]})
 
     * if callback_params={'': ((opt1, False), (opt2, False))}
 
+      - two single options
+          opt1 = 11
+          opt2 = 12
+          => calculate(<function func at 0x217a320>, [11, 12], {})
+
       - a multi option with a simple option
           opt1 == [1, 2, 3]
-          opt2 == 11
-          => calculate(1, 11)
-          => calculate(2, 11)
-          => calculate(3, 11)
+          opt2 == 12
+          => calculate(<function func at 0x2153320>, [[1, 2, 3], 12], {})
 
       - a multi option with an other multi option but with same length
           opt1 == [1, 2, 3]
           opt2 == [11, 12, 13]
-          => calculate(1, 11)
-          => calculate(2, 12)
-          => calculate(3, 13)
+          => calculate(<function func at 0x1981320>, [[1, 2, 3], [11, 12, 13]], {})
 
       - a multi option with an other multi option but with different length
           opt1 == [1, 2, 3]
           opt2 == [11, 12]
-          => ConfigError()
+          => calculate(<function func at 0x2384320>, [[1, 2, 3], [11, 12]], {})
 
       - a multi option without value with a simple option
           opt1 == []
           opt2 == 11
-          => []
+          => calculate(<function func at 0xb65320>, [[], 12], {})
 
     * if callback_params={'value': ((opt1, False), (opt2, False))}
-      => ConfigError()
+      => raises ValueError()
 
     If index is not None, return a value, otherwise return:
 
@@ -129,41 +144,42 @@ def carry_out_calculation(name, config, callback, callback_params,
     # multi's option should have same value for all option
     len_multi = None
 
-    if callback_params != []:
-        for callbacks in callback_params:
-            key = callbacks.name
-            for callbk in callbacks.params:
-                if callbk.option is not None:
-                    # callbk is something link (opt, True|False)
-                    option = callbk.get_option(config)
-                    force_permissive = callbk.force_permissive
-                    path = config.cfgimpl_get_description().impl_get_path_by_opt(
-                        option)
-                    # get value
-                    try:
-                        value = config._getattr(path, force_permissive=True)
-                    except PropertiesOptionError as err:
-                        if force_permissive:
-                            continue
-                        raise ConfigError(_('unable to carry out a calculation, '
-                                            'option {0} has properties: {1} for: '
-                                            '{2}').format(option.impl_getname(),
-                                                        err.proptype,
-                                                        name))
-                    is_multi = option.impl_is_multi()
-                    if is_multi:
-                        len_value = len(value)
-                        if len_multi is not None and len_multi != len_value:
-                            raise ConfigError(_('unable to carry out a '
-                                                'calculation, option value with'
-                                                ' multi types must have same '
-                                                'length for: {0}').format(name))
-                        len_multi = len_value
-                        one_is_multi = True
-                    tcparams.setdefault(key, []).append((value, is_multi))
-                else:
-                    # callbk is a value and not a multi
-                    tcparams.setdefault(key, []).append((callbk.value, False))
+    for key, callbacks in callback_params.items():
+        for callbk in callbacks:
+            if isinstance(callbk, tuple):
+                # callbk is something link (opt, True|False)
+                opt, force_permissive = callbk
+                path = config.cfgimpl_get_description().impl_get_path_by_opt(
+                    opt)
+                # get value
+                try:
+                    value = config._getattr(path, force_permissive=True)
+                except PropertiesOptionError as err:
+                    if force_permissive:
+                        continue
+                    raise ConfigError(_('unable to carry out a calculation, '
+                                        'option {0} has properties: {1} for: '
+                                        '{2}').format(opt._name,
+                                                      err.proptype,
+                                                      option._name))
+
+                is_multi = False
+                if opt.impl_is_multi():
+                    #opt is master, search if option is a slave
+                    if opt.impl_get_multitype() == multitypes.master:
+                        if option in opt.impl_get_master_slaves():
+                            is_multi = True
+                    #opt is slave, search if option is an other slaves
+                    elif opt.impl_get_multitype() == multitypes.slave:
+                        if option in opt.impl_get_master_slaves().impl_get_master_slaves():
+                            is_multi = True
+                if is_multi:
+                    len_multi = len(value)
+                    one_is_multi = True
+                tcparams.setdefault(key, []).append((value, is_multi))
+            else:
+                # callbk is a value and not a multi
+                tcparams.setdefault(key, []).append((callbk, False))
 
     # if one value is a multi, launch several time calculate
     # if index is set, return a value
@@ -171,16 +187,9 @@ def carry_out_calculation(name, config, callback, callback_params,
     if one_is_multi:
         ret = []
         if index:
-            if index < len_multi:
-                range_ = [index]
-            else:
-                range_ = []
-                ret = None
+            range_ = [index]
         else:
-            if max_len and max_len < len_multi:
-                range_ = range(max_len)
-            else:
-                range_ = range(len_multi)
+            range_ = range(len_multi)
         for incr in range_:
             args = []
             kwargs = {}
@@ -199,10 +208,7 @@ def carry_out_calculation(name, config, callback, callback_params,
             if index:
                 ret = calc
             else:
-                if isinstance(calc, list):
-                    ret.extend(calc)
-                else:
-                    ret.append(calc)
+                ret.append(calc)
         return ret
     else:
         # no value is multi
@@ -216,7 +222,18 @@ def carry_out_calculation(name, config, callback, callback_params,
                     args.append(couple[0])
                 else:
                     kwargs[key] = couple[0]
-        return calculate(callback, args, kwargs)
+        ret = calculate(callback, args, kwargs)
+        if callback_params != {}:
+            if isinstance(ret, list) and max_len:
+                ret = ret[:max_len]
+                if len(ret) < max_len:
+                    ret = ret + [None] * (max_len - len(ret))
+            if isinstance(ret, list) and index:
+                if len(ret) < index + 1:
+                    ret = None
+                else:
+                    ret = ret[index]
+        return ret
 
 
 def calculate(callback, args, kwargs):
diff --git a/tiramisu/config.py b/tiramisu/config.py
index 7351dd3..ea7a6b3 100644
--- a/tiramisu/config.py
+++ b/tiramisu/config.py
@@ -253,7 +253,8 @@ class SubConfig(object):
                 force_properties=force_properties,
                 force_permissive=force_permissive)
 
-    def find(self, bytype=None, byname=None, byvalue=None, type_='option'):
+    def find(self, bytype=None, byname=None, byvalue=None, type_='option',
+             check_properties=True):
         """
             finds a list of options recursively in the config
 
@@ -265,11 +266,11 @@ class SubConfig(object):
         return self._cfgimpl_get_context()._find(bytype, byname, byvalue,
                                                  first=False,
                                                  type_=type_,
-                                                 _subpath=self.cfgimpl_get_path()
-                                                 )
+                                                 _subpath=self.cfgimpl_get_path(),
+                                                 check_properties=check_properties)
 
     def find_first(self, bytype=None, byname=None, byvalue=None,
-                   type_='option', display_error=True):
+                   type_='option', display_error=True, check_properties=True):
         """
             finds an option recursively in the config
 
@@ -280,7 +281,8 @@ class SubConfig(object):
         """
         return self._cfgimpl_get_context()._find(
             bytype, byname, byvalue, first=True, type_=type_,
-            _subpath=self.cfgimpl_get_path(), display_error=display_error)
+            _subpath=self.cfgimpl_get_path(), display_error=display_error,
+            check_properties=check_properties)
 
     def _find(self, bytype, byname, byvalue, first, type_='option',
               _subpath=None, check_properties=True, display_error=True):
diff --git a/tiramisu/option.py b/tiramisu/option.py
index ec231c9..b4db8a8 100644
--- a/tiramisu/option.py
+++ b/tiramisu/option.py
@@ -47,9 +47,7 @@ forbidden_names = ('iter_all', 'iter_group', 'find', 'find_first',
 
 def valid_name(name):
     "an option's name is a str and does not start with 'impl' or 'cfgimpl'"
-    try:
-        name = str(name)
-    except:
+    if not isinstance(name, str):
         return False
     if re.match(name_regexp, name) is None and not name.startswith('_') \
             and name not in forbidden_names \
@@ -636,7 +634,7 @@ class Option(BaseOption):
                 else:
                     validator_params = (FakeCallbackParam('', (FakeCallbackParamOption(value=val),)),)
                 # Raise ValueError if not valid
-                carry_out_calculation(self.impl_getname(), config=context,
+                carry_out_calculation(self, config=context,
                                       callback=self._validator,
                                       callback_params=validator_params)
 
@@ -674,17 +672,13 @@ class Option(BaseOption):
             do_validation(value, force_index)
         else:
             if not isinstance(value, list):
-                raise ValueError(_("which must be a list").format(value,
-                                                                  self.impl_getname()))
+                raise ValueError(_("invalid value {0} for option {1} which must be a list").format(value, self.impl_getname()))
             for index, val in enumerate(value):
                 do_validation(val, index)
 
-    def impl_getdefault(self, default_multi=False):
+    def impl_getdefault(self):
         "accessing the default value"
-        if not default_multi or not self.impl_is_multi():
-            return self._default
-        else:
-            return self.getdefault_multi()
+        return self._default
 
     def impl_getdefault_multi(self):
         "accessing the default value for a multi"
@@ -940,7 +934,7 @@ class StrOption(Option):
 
 
 if sys.version_info[0] >= 3:
-    #UnicodeOption is same has StrOption in python 3+
+    #UnicodeOption is same as StrOption in python 3+
     class UnicodeOption(StrOption):
         __slots__ = tuple()
         pass
@@ -1022,6 +1016,12 @@ class IPOption(Option):
                                        warnings_only=warnings_only)
 
     def _validate(self, value):
+        # sometimes an ip term starts with a zero
+        # but this does not fit in some case, for example bind does not like it
+        for val in value.split('.'):
+            if val.startswith("0") and len(val) > 1:
+                raise ValueError(_('invalid IP'))
+        # 'standard' validation
         try:
             IP('{0}/32'.format(value))
         except ValueError:
@@ -1533,7 +1533,6 @@ class OptionDescription(BaseOption):
             self._optiondescription_group_type = group_type
             if isinstance(group_type, groups.MasterGroupType):
                 #if master (same name has group) is set
-                identical_master_child_name = False
                 #for collect all slaves
                 slaves = []
                 master = None
@@ -1549,8 +1548,7 @@ class OptionDescription(BaseOption):
                                          "in group {1}"
                                          ": this option is not a multi"
                                          "").format(child.impl_getname(), self.impl_getname()))
-                    if child.impl_getname() == self.impl_getname():
-                        identical_master_child_name = True
+                    if child._name == self.impl_getname():
                         child._multitype = multitypes.master
                         master = child
                     else:
@@ -1559,14 +1557,18 @@ class OptionDescription(BaseOption):
                     raise ValueError(_('master group with wrong'
                                        ' master name for {0}'
                                        ).format(self.impl_getname()))
+                if master._callback is not None and master._callback[1] is not None:
+                    for key, callbacks in master._callback[1].items():
+                        for callbk in callbacks:
+                            if isinstance(callbk, tuple):
+                                if callbk[0] in slaves:
+                                    raise ValueError(_("callback of master's option shall "
+                                                       "not refered a slave's ones"))
                 master._master_slaves = tuple(slaves)
                 for child in self.impl_getchildren():
                     if child != master:
                         child._master_slaves = master
                         child._multitype = multitypes.slave
-                if not identical_master_child_name:
-                    raise ValueError(_("no child has same nom has master group"
-                                       " for: {0}").format(self.impl_getname()))
         else:
             raise ValueError(_('group_type: {0}'
                                ' not allowed').format(group_type))
diff --git a/tiramisu/setting.py b/tiramisu/setting.py
index e9449b7..f95674e 100644
--- a/tiramisu/setting.py
+++ b/tiramisu/setting.py
@@ -242,6 +242,12 @@ multitypes = MultiTypeModule()
 populate_multitypes()
 
 
+# ____________________________________________________________
+class Undefined():
+    pass
+
+
+undefined = Undefined()
 # ____________________________________________________________
 class Property(object):
     "a property is responsible of the option's value access rules"
@@ -410,10 +416,11 @@ class Settings(object):
         """
         # opt properties
         properties = copy(self._getproperties(opt_or_descr, path))
-        # remove opt permissive
-        properties -= self._p_.getpermissive(path)
-        # remove global permissive if need
         self_properties = copy(self._getproperties())
+        # remove opt permissive
+        if force_permissive is True or 'permissive' in self_properties:
+            properties -= self._p_.getpermissive(path)
+        # remove global permissive if need
         if force_permissive is True or 'permissive' in self_properties:
             properties -= self._p_.getpermissive()
         if force_permissives is not None:
diff --git a/tiramisu/value.py b/tiramisu/value.py
index 4d4b2ff..c969291 100644
--- a/tiramisu/value.py
+++ b/tiramisu/value.py
@@ -22,7 +22,7 @@ from copy import copy
 import sys
 import weakref
 from tiramisu.error import ConfigError, SlaveError
-from tiramisu.setting import owners, multitypes, expires_time
+from tiramisu.setting import owners, multitypes, expires_time, undefined
 from tiramisu.autolib import carry_out_calculation
 from tiramisu.i18n import _
 from tiramisu.option import SymLinkOption
@@ -137,7 +137,7 @@ class Values(object):
         callback, callback_params = opt.impl_get_callback()
         if callback_params is None:
             callback_params = {}
-        return carry_out_calculation(opt.impl_getname(), config=self.context(),
+        return carry_out_calculation(opt, config=self.context(),
                                      callback=callback,
                                      callback_params=callback_params,
                                      index=index, max_len=max_len)
@@ -452,8 +452,7 @@ class Multi(list):
                                 values._getcallback_value(slave, index=index),
                                 force=True)
                         else:
-                            value_slave.append(slave.impl_getdefault_multi(),
-                                               force=True)
+                            value_slave.append(undefined, force=True)
 
     def __setitem__(self, index, value):
         self._validate(value, index)
@@ -461,7 +460,7 @@ class Multi(list):
         super(Multi, self).__setitem__(index, value)
         self.context().cfgimpl_get_values()._setvalue(self.opt, self.path, self)
 
-    def append(self, value, force=False):
+    def append(self, value=undefined, force=False):
         """the list value can be updated (appened)
         only if the option is a master
         """
@@ -471,12 +470,14 @@ class Multi(list):
                                    " which is a slave").format(self.opt.impl_getname()))
             elif self.opt.impl_get_multitype() == multitypes.master:
                 values = self.context().cfgimpl_get_values()
-                if value is None and self.opt.impl_has_callback():
+                if value is undefined and self.opt.impl_has_callback():
                     value = values._getcallback_value(self.opt)
                     #Force None il return a list
                     if isinstance(value, list):
                         value = None
         index = self.__len__()
+        if value is undefined:
+            value = self.opt.impl_getdefault_multi()
         self._validate(value, index)
         super(Multi, self).append(value)
         self.context().cfgimpl_get_values()._setvalue(self.opt, self.path,
diff --git a/translations/fr/tiramisu.po b/translations/fr/tiramisu.po
index ec9e66d..bff777c 100644
--- a/translations/fr/tiramisu.po
+++ b/translations/fr/tiramisu.po
@@ -116,8 +116,8 @@ msgid "invalid value for option {0}: {1}"
 msgstr "valeur invalide pour l'option {0} : {1}"
 
 #: tiramisu/option.py:454
-msgid "which must be a list"
-msgstr "lequel doit être une liste"
+msgid ""invalid value {0} for option {1} which must be a list"
+msgstr "valeur invalide pour l'option {0} : {1} laquelle doit être une liste"
 
 #: tiramisu/option.py:514
 msgid "consistency should be set with an option"