diff --git a/attributs.py b/attributs.py
index f2846eb..8cafe53 100644
--- a/attributs.py
+++ b/attributs.py
@@ -267,19 +267,25 @@ class solde(Attr):
 
     def parse_value(self, solde, ldif):
         # on évite les dépassements
-        assert 0. >= float(solde) and float(solde) <= 1024.
+        if float(solde) >= config.impression.decouvert and float(solde) <= 1024.:
+            raise ValueError("Solde invalide: %s" % solde)
         self.value = solde
 
-class host(Attr):
+class dnsAttr(Attr):
+    def parse_value(self, dns, ldif):
+        dns = dns.lower()
+        name, net = dns.split('.', 1)
+        if (net not in ['crans.org', 'wifi.crans.org'] or
+            not re.match('[a-z][-_a-z0-9]+', name)):
+            raise ValueError("Nom d'hote invalide '%s'" % dns)
+        self.value = dns
+
+
+class host(dnsAttr):
     singlevalue = True
     optional = False
     hname = legend = u"Nom d'hôte"
 
-    def parse_value(self, dns, ldif):
-        dns = dns.lower()
-        assert dns.endswith('.crans.org')
-        assert re.match('[a-z][-_a-z0-9]+', dns)
-        self.value = dns
 
 class macAddress(Attr):
     singlevalue = True
@@ -293,6 +299,7 @@ class macAddress(Attr):
     def __unicode__(self):
         return unicode(self.value)
 
+
 class ipHostNumber(Attr):
     singlevalue = True
     optional = False
@@ -307,6 +314,7 @@ class ipHostNumber(Attr):
     def __unicode__(self):
         return unicode(self.value)
 
+
 class mid(Attr):
     singlevalue = True
     optional = False
@@ -318,16 +326,12 @@ class mid(Attr):
     def __unicode__(self):
         return unicode(int(self.value))
 
-class hostAlias(Attr):
+
+class hostAlias(dnsAttr):
     singlevalue = False
     optional = True
     legend = u'Alias de nom de machine'
 
-    def parse_value(self, dns, ldif):
-        dns = dns.lower()
-        assert dns.endswith('.crans.org')
-        assert re.match('[a-z][-_a-z0-9]+', dns)
-        self.value = dns
 
 class ipsec(Attr):
     singlevalue = False