diff --git a/tests/test_cache.py b/tests/test_cache.py
index 2911e43..f46b877 100644
--- a/tests/test_cache.py
+++ b/tests/test_cache.py
@@ -352,18 +352,6 @@ def test_cache_callback():
                                   'val3': {None: ('new2', None)},
                                   'val4': {None: ('new3', None)},
                                   'val5': {None: (['yes'], None)}})
-    cfg.option('val5').value.set([undefined, 'new4'])
-    compare(values.get_cached(), {'val1': {None: ('new', None)},
-                                  'val2': {None: ('new', None)},
-                                  'val3': {None: ('new2', None)},
-                                  'val4': {None: ('new3', None)},
-                                  'val5': {None: (['yes', 'new4'], None)}})
-    cfg.value.dict()
-    compare(values.get_cached(), {'val1': {None: ('new', None)},
-                                  'val2': {None: ('new', None)},
-                                  'val3': {None: ('new2', None)},
-                                  'val4': {None: ('new3', None)},
-                                  'val5': {None: (['yes', 'new4'], None)}})
 #    assert not list_sessions()
 
 
@@ -394,7 +382,7 @@ def test_cache_leader_and_followers():
     # len is 0 so don't get any value
     compare(values.get_cached(), {'val1.val1': {None: ([], None)}})
     #
-    cfg.option('val1.val1').value.set([undefined])
+    cfg.option('val1.val1').value.set([None])
     val_val2_props = {idx_val2: (val1_val2_props, None), None: (set(), None)}
     compare(settings.get_cached(), {None: {None: (set(global_props), None)},
                                     'val1.val1': {None: (val1_val1_props, None)},
@@ -412,7 +400,7 @@ def test_cache_leader_and_followers():
     compare(values.get_cached(), {'val1.val1': {None: ([None], None)},
                                   'val1.val2': {idx_val2: (val_val2, None)},
                                   })
-    cfg.option('val1.val1').value.set([undefined, undefined])
+    cfg.option('val1.val1').value.set([None, None])
     cfg.value.dict()
     cfg.option('val1.val2', 1).value.set('oui')
     compare(settings.get_cached(), {None: {None: (set(['cache', 'disabled', 'frozen', 'hidden', 'validator', 'warnings', 'force_store_value']), None)}})
@@ -444,7 +432,7 @@ def test_cache_leader_callback():
                                     'val1.val1': {None: (val1_val1_props, None)},
                                     })
     compare(values.get_cached(), {'val1.val1': {None: ([], None)}})
-    cfg.option('val1.val1').value.set([undefined])
+    cfg.option('val1.val1').value.set([None])
     compare(settings.get_cached(), {None: {None: (set(global_props), None)},
                                     'val1.val1': {None: (val1_val1_props, None)},
                                     })
diff --git a/tests/test_config.py b/tests/test_config.py
index 148c2cc..d151ea3 100644
--- a/tests/test_config.py
+++ b/tests/test_config.py
@@ -264,12 +264,12 @@ def test_get_modified_values():
     compare(cfg.value.exportation(), {'od.g5': {None: ['yes', 'user']}})
     cfg.option('od.g4').value.set(False)
     compare(cfg.value.exportation(), {'od.g5': {None: ['yes', 'user']}, 'od.g4': {None: [False, 'user']}})
-    cfg.option('od.g4').value.set(undefined)
+    cfg.option('od.g4').value.set(True)
     compare(cfg.value.exportation(), {'od.g5': {None: ['yes', 'user']}, 'od.g4': {None: [True, 'user']}})
     cfg.option('od.g4').value.reset()
     compare(cfg.value.exportation(), {'od.g5': {None: ['yes', 'user']}})
     assert cfg.option('od.g6').ismulti()
-    cfg.option('od.g6').value.set([undefined])
+    cfg.option('od.g6').value.set([None])
     compare(cfg.value.exportation(), {'od.g5': {None: ['yes', 'user']}, 'od.g6': {None: [[None], 'user']}})
     cfg.option('od.g6').value.set([])
     compare(cfg.value.exportation(), {'od.g5': {None: ['yes', 'user']}, 'od.g6': {None: [[], 'user']}})
@@ -329,10 +329,10 @@ def test_config_multi(config_type):
     cfg = get_config(cfg, config_type)
     assert cfg.option('test1').value.get() == []
     assert cfg.option('test2').value.get() == []
-    cfg.option('test2').value.set([undefined])
+    cfg.option('test2').value.set([1])
     assert cfg.option('test2').value.get() == [1]
     assert cfg.option('test3').value.get() == [2]
-    cfg.option('test3').value.set([undefined, undefined])
+    cfg.option('test3').value.set([2, 1])
     assert cfg.option('test3').value.get() == [2, 1]
 #    assert not list_sessions()
 
diff --git a/tests/test_mandatory.py b/tests/test_mandatory.py
index a5624b3..f568434 100644
--- a/tests/test_mandatory.py
+++ b/tests/test_mandatory.py
@@ -6,7 +6,7 @@ do_autopath()
 import pytest
 from tiramisu import Config
 from tiramisu import IntOption, StrOption, OptionDescription, DynOptionDescription, PasswordOption, UsernameOption, \
-                     SymLinkOption, Leadership, undefined, Calculation, Params, \
+                     SymLinkOption, Leadership, Calculation, Params, \
                      ParamOption, ParamValue, ParamIndex, calc_value
 from tiramisu.error import PropertiesOptionError, ConfigError
 from tiramisu.setting import groups
@@ -457,7 +457,7 @@ def test_mandatory_leader_empty():
     cfg.property.read_write()
     assert cfg.option('ip_admin_eth0.ip_admin_eth0').value.get() == []
     #
-    cfg.option('ip_admin_eth0.ip_admin_eth0').value.set([undefined])
+    cfg.option('ip_admin_eth0.ip_admin_eth0').value.set([None])
     assert cfg.option('ip_admin_eth0.ip_admin_eth0').value.get() == [None]
     assert cfg.option('ip_admin_eth0.netmask_admin_eth0', 0).value.get() == None
     cfg.property.read_only()
@@ -503,7 +503,7 @@ def test_mandatory_warnings_leader_empty():
     od1 = OptionDescription('o', '', [interface1])
     cfg = Config(od1) 
     cfg.property.read_write()
-    cfg.option('ip_admin_eth0.ip_admin_eth0').value.set([undefined])
+    cfg.option('ip_admin_eth0.ip_admin_eth0').value.set([None])
     assert cfg.option('ip_admin_eth0.ip_admin_eth0').value.get() == [None]
     assert cfg.option('ip_admin_eth0.netmask_admin_eth0', 0).value.get() == None
     compare(cfg.value.mandatory(), ['ip_admin_eth0.ip_admin_eth0'])
diff --git a/tests/test_option_callback.py b/tests/test_option_callback.py
index 96003a6..620814f 100644
--- a/tests/test_option_callback.py
+++ b/tests/test_option_callback.py
@@ -299,6 +299,23 @@ def test_callback(config_type):
 #    assert not list_sessions()
 
 
+def test_callback_set(config_type):
+    val1 = StrOption('val1', "")
+    val2 = StrOption('val2', "")
+    od1 = OptionDescription('rootconfig', '', [val1, val2])
+    cfg = Config(od1)
+    cfg.property.read_write()
+    cfg = get_config(cfg, config_type)
+    cfg.option('val2').value.set(Calculation(return_value, Params(ParamOption(val1))))
+    assert cfg.option('val2').value.get() == None
+    #
+    cfg.option('val1').value.set('new-val')
+    assert cfg.option('val2').value.get() == 'new-val'
+    #
+    cfg.option('val1').value.reset()
+    assert cfg.option('val2').value.get() == None
+
+
 def test_params():
     with pytest.raises(ValueError):
         Params('str')
@@ -541,6 +558,21 @@ def test_callback_multi(config_type):
 #    assert not list_sessions()
 
 
+def test_callback_multi_set(config_type):
+    val1 = StrOption('val1', "", multi=True)
+    od1 = OptionDescription('rootconfig', '', [val1])
+    cfg = Config(od1)
+    cfg.property.read_write()
+    cfg = get_config(cfg, config_type)
+    assert cfg.option('val1').value.get() == []
+    #
+    cfg.option('val1').value.set([Calculation(return_val)])
+    assert cfg.option('val1').value.get() == ['val']
+    cfg.option('val1').value.reset()
+    assert cfg.option('val1').value.get() == []
+#    assert not list_sessions()
+
+
 def test_callback_multi_value(config_type):
     val1 = StrOption('val1', "", ['val'], multi=True)
     option = ParamOption(val1)
@@ -577,6 +609,30 @@ def test_callback_multi_value(config_type):
 #    assert not list_sessions()
 
 
+def test_callback_multi_value_set(config_type):
+    val1 = StrOption('val1', "", ['val1'], multi=True)
+    val2 = StrOption('val2', "", ['val2'], multi=True)
+    od1 = OptionDescription('rootconfig', '', [val1, val2])
+    cfg = Config(od1)
+    cfg.property.read_write()
+    cfg = get_config(cfg, config_type)
+    assert cfg.option('val1').value.get() == ['val1']
+    assert cfg.option('val2').value.get() == ['val2']
+    #
+    cfg.option('val2').value.set(Calculation(return_value, Params(ParamOption(val1))))
+    assert cfg.option('val1').value.get() == ['val1']
+    assert cfg.option('val2').value.get() == ['val1']
+    #
+    cfg.option('val1').value.set(['val1', 'yes'])
+    assert cfg.option('val2').value.get() == ['val1', 'yes']
+    assert cfg.option('val2').value.get() == ['val1', 'yes']
+    #
+    cfg.option('val2').value.reset()
+    assert cfg.option('val1').value.get() == ['val1', 'yes']
+    assert cfg.option('val2').value.get() == ['val2']
+#    assert not list_sessions()
+
+
 def test_callback_multi_list(config_type):
     val1 = StrOption('val1', "", Calculation(return_list), multi=True, properties=('notunique',))
     od1 = OptionDescription('rootconfig', '', [val1])
@@ -611,7 +667,7 @@ def test_callback_multi_callback(config_type):
     cfg.property.read_write()
     cfg = get_config(cfg, config_type)
     assert cfg.option('val1.val1').value.get() == ['val']
-    cfg.option('val1.val1').value.set(['val1', undefined])
+    cfg.option('val1.val1').value.set(['val1', None])
     assert cfg.option('val1.val1').value.get() == ['val1', None]
 #    assert not list_sessions()
 
@@ -624,27 +680,53 @@ def test_callback_multi_callback_default(config_type):
     cfg.property.read_write()
     cfg = get_config(cfg, config_type)
     assert cfg.option('val1.val1').value.get() == []
-    cfg.option('val1.val1').value.set(['val1', undefined])
+    cfg.option('val1.val1').value.set(['val1', 'val'])
     assert cfg.option('val1.val1').value.get() == ['val1', 'val']
 #    assert not list_sessions()
 
 
 def test_callback_leader_and_followers_leader(config_type):
-    val1 = StrOption('val1', "", default=[Calculation(return_val)], default_multi=Calculation(return_val), multi=True, properties=('notunique',))
-    val2 = StrOption('val2', "", multi=True)
-    interface1 = Leadership('val1', '', [val1, val2])
-    od1 = OptionDescription('rootconfig', '', [interface1])
+    val1 = StrOption('val1', "", default=['val'], multi=True)
+    val2 = StrOption('val2', "", default=Calculation(return_value, Params(ParamOption(val1))), default_multi=Calculation(return_val), multi=True, properties=('notunique',))
+    val3 = StrOption('val3', "", multi=True)
+    interface1 = Leadership('val2', '', [val2, val3])
+    od1 = OptionDescription('rootconfig', '', [val1, interface1])
     cfg = Config(od1)
     cfg.property.read_write()
     cfg = get_config(cfg, config_type)
-    assert cfg.option('val1.val1').value.get() == ['val']
-    cfg.option('val1.val1').value.set([undefined, undefined])
-    assert cfg.option('val1.val1').value.get() == ['val', 'val']
-    assert cfg.option('val1.val2', 0).value.get() == None
-    assert cfg.option('val1.val2', 1).value.get() == None
+    assert cfg.option('val1').value.get() == ['val']
+    assert cfg.option('val2.val2').value.get() == ['val']
+    #
+    cfg.option('val1').value.set(['val1', 'val2'])
+    assert cfg.option('val1').value.get() == ['val1', 'val2']
+    assert cfg.option('val2.val2').value.get() == ['val1', 'val2']
+    assert cfg.option('val2.val3', 0).value.get() == None
+    assert cfg.option('val2.val3', 1).value.get() == None
+    #
+    cfg.option('val1').value.set(['val'])
+    assert cfg.option('val2.val2').value.get() == ['val']
+    assert cfg.option('val2.val3', 0).value.get() == None
 #    assert not list_sessions()
 
 
+def test_callback_leader_and_followers_leader_set(config_type):
+    val1 = StrOption('val1', "", default=['val1', 'val2'], multi=True)
+    val2 = StrOption('val2', "", multi=True)
+    val3 = StrOption('val3', "", multi=True)
+    interface1 = Leadership('val2', '', [val2, val3])
+    od1 = OptionDescription('rootconfig', '', [val1, interface1])
+    cfg = Config(od1)
+    cfg.property.read_write()
+    cfg = get_config(cfg, config_type)
+    assert cfg.option('val1').value.get() == ['val1', 'val2']
+    #
+    cfg.option('val2.val2').value.set(Calculation(return_value, Params(ParamOption(val1))))
+    assert cfg.option('val2.val2').value.get() == ['val1', 'val2']
+    assert cfg.option('val2.val3', 0).value.get() == None
+    assert cfg.option('val2.val3', 1).value.get() == None
+    #assert not list_sessions()
+
+
 def test_callback_follower(config_type):
     val1 = StrOption('val1', "", multi=True)
     val2 = StrOption('val2', "", Calculation(return_value3, Params(ParamValue(['string', 'new']), {'index': ParamIndex()})), multi=True)
@@ -670,6 +752,28 @@ def test_callback_follower(config_type):
 #    assert not list_sessions()
 
 
+def test_callback_follower_set(config_type):
+    val1 = StrOption('val1', "")
+    val2 = StrOption('val2', "", default=['val1'], multi=True)
+    val3 = StrOption('val3', "", multi=True)
+    interface1 = Leadership('val2', '', [val2, val3])
+    od1 = OptionDescription('rootconfig', '', [val1, interface1])
+    cfg = Config(od1)
+    cfg.property.read_write()
+    cfg = get_config(cfg, config_type)
+    cfg.option('val1').value.set('val')
+    assert cfg.option('val1').value.get() == 'val'
+    assert cfg.option('val2.val2').value.get() == ['val1']
+    assert cfg.option('val2.val3', 0).value.get() == None
+    #
+    cfg.option('val2.val3', 0).value.set(Calculation(return_value, Params(ParamOption(val1))))
+    assert cfg.option('val2.val3', 0).value.get() == 'val'
+    #
+    cfg.option('val1').value.set('val1')
+    assert cfg.option('val2.val3', 0).value.get() == 'val1'
+#    assert not list_sessions()
+
+
 def test_callback_leader_and_followers_leader2(config_type):
     val1 = StrOption('val1', "", multi=True)
     val2 = StrOption('val2', "", multi=True, default_multi='val2')
@@ -704,7 +808,7 @@ def test_callback_leader_and_followers_leader_mandatory1(config_type):
         cfg.send()
     cfg_ori.property.read_write()
     cfg = get_config(cfg_ori, config_type)
-    cfg.option('val1.val1').value.set([undefined, 'val3'])
+    cfg.option('val1.val1').value.set(['val', 'val3'])
     if config_type == 'tiramisu-api':
         cfg.send()
     cfg_ori.property.read_only()
@@ -860,7 +964,8 @@ def test_callback_leader_and_followers_leader_list(config_type):
     assert cfg.option('val1.val1').value.get() == ['val', 'val']
     assert cfg.option('val1.val2', 0).value.get() == None
     assert cfg.option('val1.val2', 1).value.get() == None
-    cfg.option('val1.val1').value.set(['val', 'val', undefined])
+    default_multi = cfg.option('val1.val1').defaultmulti()
+    cfg.option('val1.val1').value.set(['val', 'val', default_multi])
     assert cfg.option('val1.val1').value.get() == ['val', 'val', None]
     assert cfg.option('val1.val2', 0).value.get() == None
     assert cfg.option('val1.val2', 1).value.get() == None
diff --git a/tests/test_option_default.py b/tests/test_option_default.py
index 965b3d3..5ff883b 100644
--- a/tests/test_option_default.py
+++ b/tests/test_option_default.py
@@ -115,8 +115,10 @@ def test_force_default_on_freeze_multi():
     cfg_ori.property.read_write()
     cfg = cfg_ori
     # FIXME cfg = get_config(cfg_ori, config_type)
-    cfg.option('dummy1').value.set([undefined, True])
-    cfg.option('dummy2').value.set([undefined, False])
+    default = cfg.option('dummy1').value.default()[0]
+    cfg.option('dummy1').value.set([default, True])
+    default = cfg.option('dummy2').value.default()[0]
+    cfg.option('dummy2').value.set([default, False])
     owner = cfg.owner.get()
     assert cfg.option('dummy1').owner.get() == owner
     assert cfg.option('dummy2').owner.get() == owner
diff --git a/tests/test_option_setting.py b/tests/test_option_setting.py
index 1cdf17b..85aca5d 100644
--- a/tests/test_option_setting.py
+++ b/tests/test_option_setting.py
@@ -143,7 +143,7 @@ def test_setitem(config_type):
     od1 = OptionDescription("options", "", [s])
     cfg = Config(od1)
     cfg = get_config(cfg, config_type)
-    cfg.option('string').value.set([undefined, 'foo'])
+    cfg.option('string').value.set(['string', 'foo'])
     assert cfg.option('string').value.get() == ['string', 'foo']
 #    assert not list_sessions()
 
diff --git a/tests/test_option_validator.py b/tests/test_option_validator.py
index 8c313fa..40c26ba 100644
--- a/tests/test_option_validator.py
+++ b/tests/test_option_validator.py
@@ -8,7 +8,7 @@ from tiramisu import BoolOption, StrOption, IPOption, NetmaskOption, NetworkOpti
         IntOption, OptionDescription, Leadership, Config, Params, ParamValue, ParamOption, \
         ParamSelfOption, ParamIndex, ParamInformation, ParamSelfInformation, ParamSelfOption, Calculation, \
         valid_ip_netmask, valid_network_netmask, \
-        valid_in_network, valid_broadcast, valid_not_equal, undefined
+        valid_in_network, valid_broadcast, valid_not_equal
 from tiramisu.setting import groups
 from tiramisu.error import ValueErrorWarning, ConfigError, PropertiesOptionError
 from tiramisu.i18n import _
@@ -713,7 +713,7 @@ def test_validator_network_netmask_multi_follower_default_multi(config_type):
     cfg = Config(od2)
     cfg.property.read_write()
     cfg = get_config(cfg, config_type)
-    cfg.option('a.a').value.set([undefined])
+    cfg.option('a.a').value.set(['192.168.1.0'])
     assert cfg.option('a.a').value.get() == ['192.168.1.0']
     assert cfg.option('a.b', 0).value.get() == '255.255.255.0'
 #    assert not list_sessions()
@@ -745,10 +745,10 @@ def test_validator_network_netmask_multi_follower_default(config_type):
         cfg.option('a.b', 0).value.set([u'192.168.1.0'])
     with pytest.raises(ValueError):
         cfg.option('a.b', 1).value.set([u'192.168.1.1'])
-    cfg.option('a.a').value.set(['192.168.1.0', undefined])
+    cfg.option('a.a').value.set(['192.168.1.0', '192.168.1.1'])
     cfg.option('a.b', 0).value.set('255.255.255.0')
     cfg.option('a.b', 1).value.set('255.255.255.255')
-    cfg.option('a.a').value.set([u'192.168.1.0', u'192.168.1.1'])
+    cfg.option('a.a').value.set(['192.168.1.0', '192.168.1.1'])
 #    assert not list_sessions()
 
 
@@ -790,7 +790,7 @@ def test_validator_network_netmask_multi_follower_callback(config_type):
     cfg.option('a.b', 0).value.get()
     with pytest.raises(ValueError):
         cfg.option('a.b', 1).value.get()
-    cfg.option('a.a').value.set(['192.168.1.0', undefined])
+    cfg.option('a.a').value.set(['192.168.1.0', '192.168.1.1'])
     cfg.option('a.b', 0).value.set('255.255.255.0')
     cfg.option('a.b', 1).value.set('255.255.255.255')
     cfg.option('a.a').value.set(['192.168.1.0', '192.168.1.1'])
diff --git a/tests/test_submulti.py b/tests/test_submulti.py
index 93d5a3d..4e2f1b2 100644
--- a/tests/test_submulti.py
+++ b/tests/test_submulti.py
@@ -7,7 +7,7 @@ import warnings
 
 from tiramisu.setting import groups, owners
 from tiramisu import StrOption, IntOption, OptionDescription, submulti, Leadership, Config, \
-                     MetaConfig, undefined, Params, ParamOption, Calculation
+                     MetaConfig, Params, ParamOption, Calculation
 from tiramisu.error import LeadershipError, PropertiesOptionError
 
 
@@ -107,26 +107,26 @@ def test_append_submulti():
     owner = cfg.owner.get()
     assert cfg.option('multi').value.get() == []
     assert cfg.option('multi').owner.get() == owners.default
-    cfg.option('multi').value.set([undefined])
+    cfg.option('multi').value.set([[]])
     assert cfg.option('multi').owner.get() == owner
     assert cfg.option('multi').value.get() == [[]]
-    cfg.option('multi').value.set([undefined, ['no']])
+    cfg.option('multi').value.set([[], ['no']])
     assert cfg.option('multi').value.get() == [[], ['no']]
     #
     assert cfg.option('multi2').value.get() == []
     assert cfg.option('multi2').owner.get() == owners.default
-    cfg.option('multi2').value.set([undefined])
+    cfg.option('multi2').value.set([cfg.option('multi2').defaultmulti()])
     assert cfg.option('multi2').owner.get() == owner
     assert cfg.option('multi2').value.get() == [['yes']]
-    cfg.option('multi2').value.set([undefined, ['no']])
+    cfg.option('multi2').value.set([cfg.option('multi2').defaultmulti(), ['no']])
     assert cfg.option('multi2').value.get() == [['yes'], ['no']]
     #
     assert cfg.option('multi3').value.get() == [['yes']]
     assert cfg.option('multi3').owner.get() == owners.default
-    cfg.option('multi3').value.set([undefined, undefined])
+    cfg.option('multi3').value.set([cfg.option('multi2').defaultmulti(), []])
     assert cfg.option('multi3').owner.get() == owner
     assert cfg.option('multi3').value.get() == [['yes'], []]
-    cfg.option('multi3').value.set([undefined, undefined, ['no']])
+    cfg.option('multi3').value.set([cfg.option('multi2').defaultmulti(), [], ['no']])
     assert cfg.option('multi3').value.get() == [['yes'], [], ['no']]
 #    assert not list_sessions()
 
@@ -193,7 +193,7 @@ def test_callback_submulti_str():
     owner = cfg.owner.get()
     assert cfg.option('multi').owner.get() == owners.default
     assert cfg.option('multi').value.get() == [['val']]
-    cfg.option('multi').value.set([['val'], undefined])
+    cfg.option('multi').value.set([['val'], cfg.option('multi').defaultmulti()])
     assert cfg.option('multi').owner.get() == owner
     assert cfg.option('multi').value.get() == [['val'], ['val']]
     cfg.option('multi').value.reset()
@@ -209,13 +209,13 @@ def test_callback_submulti_list():
     owner = cfg.owner.get()
     assert cfg.option('multi').value.get() == [['val', 'val']]
     assert cfg.option('multi').owner.get() == owners.default
-    cfg.option('multi').value.set([['val', 'val'], undefined])
-    #assert cfg.option('multi').owner.get() == owner
-    #assert cfg.option('multi').value.get() == [['val', 'val'], ['val', 'val']]
-    #cfg.option('multi').value.set([['val', 'val'], undefined, undefined])
-    #assert cfg.option('multi').value.get() == [['val', 'val'], ['val', 'val'], ['val', 'val']]
-    #cfg.option('multi').value.reset()
-    #assert cfg.option('multi').owner.get() == owners.default
+    cfg.option('multi').value.set([['val', 'val'], cfg.option('multi').defaultmulti()])
+    assert cfg.option('multi').owner.get() == owner
+    assert cfg.option('multi').value.get() == [['val', 'val'], ['val', 'val']]
+    cfg.option('multi').value.set([['val', 'val'], cfg.option('multi').defaultmulti(), cfg.option('multi').defaultmulti()])
+    assert cfg.option('multi').value.get() == [['val', 'val'], ['val', 'val'], ['val', 'val']]
+    cfg.option('multi').value.reset()
+    assert cfg.option('multi').owner.get() == owners.default
 #    assert not list_sessions()
 
 
@@ -227,7 +227,7 @@ def test_callback_submulti_list_list():
     owner = cfg.owner.get()
     assert cfg.option('multi').value.get() == [['val', 'val']]
     assert cfg.option('multi').owner.get() == owners.default
-    cfg.option('multi').value.set([['val', 'val'], undefined])
+    cfg.option('multi').value.set([['val', 'val'], cfg.option('multi').defaultmulti()])
     assert cfg.option('multi').owner.get() == owner
     assert cfg.option('multi').value.get() == [['val', 'val'], []]
     cfg.option('multi').value.reset()
diff --git a/tiramisu/api.py b/tiramisu/api.py
index 289a7d4..46bce7f 100644
--- a/tiramisu/api.py
+++ b/tiramisu/api.py
@@ -28,6 +28,7 @@ from .setting import ConfigBag, OptionBag, owners, groups, undefined, \
 from .config import KernelConfig, KernelGroupConfig, KernelMetaConfig, KernelMixConfig
 from .option import RegexpOption, OptionDescription, ChoiceOption
 from .todict import TiramisuDict
+from .autolib import Calculation
 
 
 TIRAMISU_VERSION = 4
@@ -615,15 +616,7 @@ class TiramisuOptionValue(CommonTiramisuOption):
         """Change option's value"""
         option_bag = options_bag[-1]
         values = option_bag.config_bag.context.get_values()
-        if isinstance(value, list):
-            while undefined in value:
-                idx = value.index(undefined)
-                soption_bag = option_bag.copy()
-                soption_bag.index = idx
-                value[idx] = values.get_default_value(soption_bag)
-        elif value == undefined:
-            value = values.get_default_value(option_bag)
-        if option_bag.option.impl_is_leader() and \
+        if not isinstance(value, Calculation) and option_bag.option.impl_is_leader() and \
                 len(value) < self._config_bag.context.get_length_leadership(options_bag[-2]):
             raise LeadershipError(_('cannot reduce length of the leader "{}"'
                                     '').format(option_bag.option.impl_get_display_name()))
diff --git a/tiramisu/autolib.py b/tiramisu/autolib.py
index e355955..91e9ece 100644
--- a/tiramisu/autolib.py
+++ b/tiramisu/autolib.py
@@ -212,6 +212,9 @@ class Calculation:
                                      for_settings=for_settings,
                                      )
 
+    def __deepcopy__(x, memo):
+        return x
+
 
 def manager_callback(callback: Callable,
                      param: Param,
diff --git a/tiramisu/config.py b/tiramisu/config.py
index e12387d..318a715 100644
--- a/tiramisu/config.py
+++ b/tiramisu/config.py
@@ -31,6 +31,7 @@ from .setting import OptionBag, ConfigBag, Settings, undefined, groups
 from .value import Values, owners
 from .i18n import _
 from .cacheobj import Cache
+from .autolib import Calculation
 
 
 class _SubConfig:
diff --git a/tiramisu/option/leadership.py b/tiramisu/option/leadership.py
index 9737e52..ff677e2 100644
--- a/tiramisu/option/leadership.py
+++ b/tiramisu/option/leadership.py
@@ -186,7 +186,7 @@ class Leadership(OptionDescription):
                                                   )
                     values.set_storage_value(foption_bag_index.path,
                                              index,
-                                             values.get_value(foption_bag_index),
+                                             values.get_value(foption_bag_index)[0],
                                              owner,
                                              )
 
diff --git a/tiramisu/option/optiondescription.py b/tiramisu/option/optiondescription.py
index 0d31088..72c5e50 100644
--- a/tiramisu/option/optiondescription.py
+++ b/tiramisu/option/optiondescription.py
@@ -144,7 +144,7 @@ class CacheOptionDescription(BaseOption):
                 leader = option.impl_get_leadership().get_leader()
                 for leader_option_bag in do_option_bags(leader):
                     leader_option_bag.properties = frozenset()
-                    follower_len = len(values.get_value(leader_option_bag))
+                    follower_len = len(values.get_value(leader_option_bag)[0])
                     if option.issubdyn():
                         subpath = leader_option_bag.option.rootpath
                         doption = option.to_dynoption(subpath,
@@ -162,7 +162,7 @@ class CacheOptionDescription(BaseOption):
                                                )
                         if values.hasvalue(subpath, index=index):
                             continue
-                        value = values.get_value(option_bag)
+                        value = values.get_value(option_bag)[0]
                         if value is None:
                             continue
                         values.set_storage_value(subpath,
@@ -173,7 +173,7 @@ class CacheOptionDescription(BaseOption):
             else:
                 for option_bag in do_option_bags(option):
                     option_bag.properties = frozenset()
-                    value = values.get_value(option_bag)
+                    value = values.get_value(option_bag)[0]
                     if value is None:
                         continue
                     if values.hasvalue(option_bag.path):
diff --git a/tiramisu/value.py b/tiramisu/value.py
index d16c52b..7f337c3 100644
--- a/tiramisu/value.py
+++ b/tiramisu/value.py
@@ -65,7 +65,7 @@ class Values:
                                                      )
         # no cached value so get value
         if not is_cached:
-            value = self.get_value(option_bag)
+            value, has_calculation = self.get_value(option_bag)
         # validates and warns value
         if not validated:
             validate = option_bag.option.impl_validate(value,
@@ -78,7 +78,7 @@ class Values:
                                             check_error=False,
                                             )
         # set value to cache
-        if not is_cached:
+        if not is_cached and not has_calculation:
             cache.setcache(option_bag,
                            value,
                            validated=validate,
@@ -106,7 +106,10 @@ class Values:
             # the value is a default value
             # get it
             value = self.get_default_value(option_bag)
-        return value
+        value, has_calculation = self.get_calculated_value(option_bag,
+                                                           value,
+                                                           )
+        return value, has_calculation
 
     def get_default_value(self,
                           option_bag: OptionBag,
@@ -122,9 +125,9 @@ class Values:
             return moption_bag.config_bag.context.get_values().get_cached_value(moption_bag)
 
         # now try to get calculated value:
-        value = self.get_calculated_value(option_bag,
-                                          option_bag.option.impl_getdefault(),
-                                          )
+        value, _has_calculation = self.get_calculated_value(option_bag,
+                                                            option_bag.option.impl_getdefault(),
+                                                            )
         if option_bag.index is not None and isinstance(value, (list, tuple)) \
                 and (not option_bag.option.impl_is_submulti() or \
                 not value or isinstance(value[0], list)):
@@ -135,9 +138,9 @@ class Values:
             else:
                 # no value for this index, retrieve default multi value
                 # default_multi is already a list for submulti
-                value = self.get_calculated_value(option_bag,
-                                                  option_bag.option.impl_getdefault_multi(),
-                                                  )
+                value, _has_calculation = self.get_calculated_value(option_bag,
+                                                                    option_bag.option.impl_getdefault_multi(),
+                                                                    )
         return value
 
     def get_calculated_value(self,
@@ -147,6 +150,7 @@ class Values:
                              ) -> Any:
         """value could be a calculation, in this case do calculation
         """
+        has_calculation = False
         if isinstance(value, Calculation):
             try:
                 value = value.execute(option_bag)
@@ -154,18 +158,21 @@ class Values:
                 msg = _(f'error when calculating "{option_bag.option.impl_get_display_name()}": '
                         f'{err} : {option_bag.path}')
                 raise ConfigError(msg) from err
+            has_calculation = True
         elif isinstance(value, list):
             # if value is a list, do subcalculation
             for idx, val in enumerate(value):
-                value[idx] = self.get_calculated_value(option_bag,
-                                                       val,
-                                                       reset_cache=False,
-                                                       )
+                value[idx], _has_calculation = self.get_calculated_value(option_bag,
+                                                                         val,
+                                                                         reset_cache=False,
+                                                                         )
+                if _has_calculation:
+                    has_calculation = True
         if reset_cache:
             self.reset_cache_after_calculation(option_bag,
                                                value,
                                                )
-        return value
+        return value, has_calculation
 
     #______________________________________________________________________
     def check_force_to_metaconfig(self,
@@ -248,27 +255,31 @@ class Values:
         """set value to option
         """
         owner = self.get_context_owner()
-        if 'validator' in option_bag.config_bag.properties:
-            self.setvalue_validation(value,
-                                     option_bag,
-                                     )
+        setting_properties = option_bag.config_bag.properties
+        ori_value = value
+        if 'validator' in setting_properties:
+            value, has_calculation = self.setvalue_validation(value,
+                                                              option_bag,
+                                                              )
 
-        if isinstance(value, list):
+        elif isinstance(value, list):
             # copy
             value = value.copy()
         self._setvalue(option_bag,
-                       value,
+                       ori_value,
                        owner,
                        )
-        setting_properties = option_bag.config_bag.properties
         validator = 'validator' in setting_properties and \
                 'demoting_error_warning' not in setting_properties
-        if validator:
+        if validator and not has_calculation:
             cache = option_bag.config_bag.context.get_values_cache()
             cache.setcache(option_bag,
                            value,
                            validated=validator,
                            )
+        elif 'validator' in setting_properties and has_calculation:
+            cache = option_bag.config_bag.context.get_values_cache()
+            cache.delcache(option_bag.path)
         if 'force_store_value' in setting_properties and option_bag.option.impl_is_leader():
             leader = option_bag.option.impl_get_leadership()
             leader.follower_force_store_value(value,
@@ -286,10 +297,10 @@ class Values:
         # First validate properties with this value
         opt = option_bag.option
         settings.validate_frozen(option_bag)
-        val = self.get_calculated_value(option_bag,
-                                        value,
-                                        False,
-                                        )
+        val, has_calculation = self.get_calculated_value(option_bag,
+                                                         value,
+                                                         False,
+                                                         )
         settings.validate_mandatory(val,
                                     option_bag,
                                     )
@@ -300,10 +311,11 @@ class Values:
                           )
         if 'warnings' in option_bag.config_bag.properties:
             # No error found so emit warnings
-            opt.impl_validate(value,
+            opt.impl_validate(val,
                               option_bag,
                               check_error=False,
                               )
+        return val, has_calculation
 
     def _setvalue(self,
                   option_bag: OptionBag,
@@ -362,7 +374,7 @@ class Values:
                                                 option_bag.config_bag,
                                                 properties=frozenset(),
                                                 )
-                        indexes = range(len(self.get_value(loption_bag)))
+                        indexes = range(len(self.get_value(loption_bag)[0]))
                     else:
                         indexes = [None]
                     for index in indexes:
@@ -370,7 +382,7 @@ class Values:
                                                 index,
                                                 option_bag.config_bag,
                                                 )
-                        default_value = [self.get_value(coption_bag), owners.forced]
+                        default_value = [self.get_value(coption_bag)[0], owners.forced]
                         self._values.setdefault(coption_bag.path, {})[index] = default_value
 
     def _get_modified_parent(self,