diff --git a/tiramisu/config.py b/tiramisu/config.py
index 3687349..25dbaf9 100644
--- a/tiramisu/config.py
+++ b/tiramisu/config.py
@@ -185,7 +185,9 @@ class SubConfig(object):
             homeconfig, name = self.cfgimpl_get_home_by_path(name)
             return homeconfig.__setattr__(name, value)
         child = getattr(self.cfgimpl_get_description(), name)
-        if not isinstance(child, SymLinkOption):
+        if isinstance(child, OptionDescription):
+            raise SyntaxError(_("can't assign to an OptionDescription"))
+        elif not isinstance(child, SymLinkOption):
             if self._impl_path is None:
                 path = name
             else:
diff --git a/translations/fr/tiramisu.po b/translations/fr/tiramisu.po
index a81e14e..0075059 100644
--- a/translations/fr/tiramisu.po
+++ b/translations/fr/tiramisu.po
@@ -2,7 +2,7 @@ msgid ""
 msgstr ""
 "Project-Id-Version: \n"
 "Report-Msgid-Bugs-To: \n"
-"POT-Creation-Date: 2013-09-26 22:24+CEST\n"
+"POT-Creation-Date: 2013-09-26 22:33+CEST\n"
 "PO-Revision-Date: \n"
 "Last-Translator: Emmanuel Garette <egarette@cadoles.com>\n"
 "Language-Team: LANGUAGE <LL@li.org>\n"
@@ -41,23 +41,27 @@ msgstr ""
 "pas d'option description trouvé pour cette config (peut être une metaconfig "
 "sans meta)"
 
-#: tiramisu/config.py:318
+#: tiramisu/config.py:189
+msgid "can't assign to an OptionDescription"
+msgstr "ne peut pas attribuer une valeur à une OptionDescription"
+
+#: tiramisu/config.py:320
 msgid "unknown type_ type {0}for _find"
 msgstr "type_ type {0} pour _find inconnu"
 
-#: tiramisu/config.py:357
+#: tiramisu/config.py:359
 msgid "no option found in config with these criteria"
 msgstr "aucune option trouvée dans la config avec ces critères"
 
-#: tiramisu/config.py:407
+#: tiramisu/config.py:409
 msgid "make_dict can't filtering with value without option"
 msgstr "make_dict ne peut filtrer sur une valeur mais sans option"
 
-#: tiramisu/config.py:428
+#: tiramisu/config.py:430
 msgid "unexpected path {0}, should start with {1}"
 msgstr "chemin imprévu {0}, devrait commencer par {1}"
 
-#: tiramisu/config.py:488
+#: tiramisu/config.py:490
 msgid "opt in getowner must be an option not {0}"
 msgstr "opt dans getowner doit être une option pas {0}"
 
diff --git a/translations/tiramisu.pot b/translations/tiramisu.pot
index 7304c9f..dfd4b86 100644
--- a/translations/tiramisu.pot
+++ b/translations/tiramisu.pot
@@ -5,7 +5,7 @@
 msgid ""
 msgstr ""
 "Project-Id-Version: PACKAGE VERSION\n"
-"POT-Creation-Date: 2013-09-26 22:24+CEST\n"
+"POT-Creation-Date: 2013-09-26 22:33+CEST\n"
 "PO-Revision-Date: YEAR-MO-DA HO:MI+ZONE\n"
 "Last-Translator: FULL NAME <EMAIL@ADDRESS>\n"
 "Language-Team: LANGUAGE <LL@li.org>\n"
@@ -35,23 +35,27 @@ msgstr ""
 msgid "no option description found for this config (may be metaconfig without meta)"
 msgstr ""
 
-#: tiramisu/config.py:318
+#: tiramisu/config.py:189
+msgid "can't assign to an OptionDescription"
+msgstr ""
+
+#: tiramisu/config.py:320
 msgid "unknown type_ type {0}for _find"
 msgstr ""
 
-#: tiramisu/config.py:357
+#: tiramisu/config.py:359
 msgid "no option found in config with these criteria"
 msgstr ""
 
-#: tiramisu/config.py:407
+#: tiramisu/config.py:409
 msgid "make_dict can't filtering with value without option"
 msgstr ""
 
-#: tiramisu/config.py:428
+#: tiramisu/config.py:430
 msgid "unexpected path {0}, should start with {1}"
 msgstr ""
 
-#: tiramisu/config.py:488
+#: tiramisu/config.py:490
 msgid "opt in getowner must be an option not {0}"
 msgstr ""