diff --git a/test/test_dyn_optiondescription.py b/test/test_dyn_optiondescription.py
index 42dcfcb..b2c3416 100644
--- a/test/test_dyn_optiondescription.py
+++ b/test/test_dyn_optiondescription.py
@@ -10,7 +10,6 @@ from tiramisu import BoolOption, StrOption, ChoiceOption, IPOption, \
     OptionDescription, DynOptionDescription, DynSymLinkOption, submulti, MasterSlaves, \
     Config, Params, ParamOption, ParamValue
 from tiramisu.error import PropertiesOptionError, ConfigError, ConflictError
-from tiramisu.storage import delete_session
 
 from py.test import raises
 
diff --git a/test/test_storage.py b/test/test_storage.py
index c4b5882..a7edc80 100644
--- a/test/test_storage.py
+++ b/test/test_storage.py
@@ -27,6 +27,21 @@ def test_list():
     assert 'test_non_persistent' not in list_sessions('config')
 
 
+def test_delete_not_persisten():
+    b = BoolOption('b', '')
+    o = OptionDescription('od', '', [b])
+    try:
+        Config(o, session_id='test_persistent', persistent=True)
+    except:
+        c = Config(o, session_id='not_test_persistent')
+        assert list_sessions('all') == ['not_test_persistent']
+        del c
+        assert list_sessions('all') == []
+        #
+        c = Config(o, session_id='not_test_persistent')
+        raises(ValueError, "delete_session('not_test_persistent')")
+
+
 def test_create_persistent():
     b = BoolOption('b', '')
     o = OptionDescription('od', '', [b])
diff --git a/tiramisu/option/syndynoptiondescription.py b/tiramisu/option/syndynoptiondescription.py
index 8a6cf0d..219f5a4 100644
--- a/tiramisu/option/syndynoptiondescription.py
+++ b/tiramisu/option/syndynoptiondescription.py
@@ -103,9 +103,6 @@ class SynDynOptionDescription(object):
     def impl_get_display_name(self):
         return self._opt.impl_get_display_name() + self._suffix
 
-    def impl_getdoc(self):
-        return self._opt.impl_getdoc() + self._suffix
-
     def reset_cache(self,
                     path,
                     values,
diff --git a/tiramisu/storage/dictionary/__init__.py b/tiramisu/storage/dictionary/__init__.py
index 5d1a79f..ff61b50 100644
--- a/tiramisu/storage/dictionary/__init__.py
+++ b/tiramisu/storage/dictionary/__init__.py
@@ -24,7 +24,6 @@ use it. But if something goes wrong, you will lost your modifications.
 """
 from .value import Values
 from .setting import Properties, Permissives
-from .storage import setting, Storage, list_sessions, delete_session
+from .storage import setting, Storage, list_sessions
 
-__all__ = ('setting', 'Values', 'Properties', 'Permissives', 'Storage', 'list_sessions',
-           'delete_session')
+__all__ = ('setting', 'Values', 'Properties', 'Permissives', 'Storage', 'list_sessions')
diff --git a/tiramisu/storage/dictionary/storage.py b/tiramisu/storage/dictionary/storage.py
index 32c5747..2aef94f 100644
--- a/tiramisu/storage/dictionary/storage.py
+++ b/tiramisu/storage/dictionary/storage.py
@@ -15,7 +15,7 @@
 # along with this program.  If not, see <http://www.gnu.org/licenses/>.
 # ____________________________________________________________
 from ...i18n import _
-from ...error import ConfigError, ConflictError
+from ...error import ConflictError
 
 
 class Setting(object):
@@ -32,10 +32,6 @@ def list_sessions():  # pragma: optional cover
     return _list_sessions
 
 
-def delete_session(session_id):  # pragma: optional cover
-    raise ConfigError(_('dictionary storage cannot delete session'))
-
-
 class Storage(object):
     __slots__ = ('session_id', 'persistent')
     storage = 'dictionary'
diff --git a/tiramisu/storage/dictionary/value.py b/tiramisu/storage/dictionary/value.py
index 674b350..9289327 100644
--- a/tiramisu/storage/dictionary/value.py
+++ b/tiramisu/storage/dictionary/value.py
@@ -41,9 +41,6 @@ class Values(Cache):
     def commit(self):
         pass
 
-    def getsession(self):
-        pass
-
     def _setvalue_info(self, nb, idx, value, values, index, vidx):
         lst = list(self._values[nb])
         if idx is None:
@@ -299,4 +296,4 @@ class Values(Cache):
         self._values = export
 
 def delete_session(session_id):
-    raise ValueError(_('a dictionary cannot be persistent'))
+    raise ValueError(_('cannot delete none persistent session'))
diff --git a/tiramisu/storage/sqlite3/value.py b/tiramisu/storage/sqlite3/value.py
index de1d70d..915e429 100644
--- a/tiramisu/storage/sqlite3/value.py
+++ b/tiramisu/storage/sqlite3/value.py
@@ -34,9 +34,6 @@ class Values(Sqlite3DB):
         """
         super(Values, self).__init__(storage)
 
-    def getsession(self):
-        pass
-
     # sqlite
     def _sqlite_select(self, path, index):
         request = "SELECT value FROM value WHERE path = ? AND session_id = ? "