diff --git a/attributs.py b/attributs.py
index 76726cc..f80cd9c 100644
--- a/attributs.py
+++ b/attributs.py
@@ -104,13 +104,18 @@ class Attr(object):
         """Vérifie l'unicité dans la base de la valeur (mailAlias, chbre,
         etc...)"""
         attr = self.__class__.__name__
-        if attr in [ "mid", "uid", "cid", "fid", "aid"]:  #... etc
-            assert not self.conn.search('%s=%s' % (attr, str(self)))
-        if attr in [ "mailAlias", "canonicalAlias", 'mail', 'uid']:
+        if attr in ["mid", "uid", "cid", "fid", "aid", "ipHostNumber", "uidNumber"]:
+            res = self.conn.search('%s=%s' % (attr, str(self)))
+            if res:
+                raise ValueError("%s déjà existant" % attr, [r.dn for r in res])
+        if attr in ["mailAlias", "canonicalAlias", 'mail', 'uid']:
             res = self.conn.search('(|(mail=%s)(mailAlias=%s)(canonicalAlias=%s))' % ((str(self),)*3))
             if res:
                 raise ValueError("Mail déjà existant", [r.dn for r in res])
-            #assert not mailexist(str(self))
+        if attr in ["host", "hostAlias"]:
+            res = self.conn.search('(|(host=%s)(hostAlias=%s))' % ((str(self),)*2))
+            if res:
+                raise ValueError("Hôte déjà existant", [r.dn for r in res])
 
     def _check_users_restrictions(self, values):
         """Vérifie les restrictions supplémentaires imposées selon les