diff --git a/ccserver/handlers.py b/ccserver/handlers.py
index b7a74d995035c8fa6f9aeef658314644848a90d4..c97f291d58e1af78dbc80cd4289cb8465c69dddb 100644
--- a/ccserver/handlers.py
+++ b/ccserver/handlers.py
@@ -5,6 +5,7 @@ import inspect
 import logging
 from sjrpc.utils import RpcHandler, pure
 from tql import TqlQuery
+from conf import CCConf
 
 def listed(func):
     func.__listed__ = True
@@ -104,8 +105,9 @@ class ClientHandler(CCHandler):
 
         # Try to get vm for each matched hypervisor:
         async_calls = {}
+        tags = tuple(query.tags)
         for hy in hypervisors:
-            async_calls[hy.connection.async_call('list_vm')] = hy
+            async_calls[hy.connection.async_call('list_vm', tags=tags)] = hy
 
         logging.debug('Waiting for the response of hypervisors...')
         responses = self._server.manager.wait(frozenset(async_calls), timeout=5)
@@ -128,7 +130,11 @@ class ClientHandler(CCHandler):
                     objects.append(vm_tags)
         # Filter the objects with the query, and return it:
         return query.filter(objects)
-        
+
+
+class AuthenticationError(Exception):
+    pass
+
 
 class WelcomeHandler(CCHandler):
     '''
@@ -147,11 +153,14 @@ class WelcomeHandler(CCHandler):
         '''
         Authenticate the client.
         '''
+        try:
+            role = self._server.conf.authentify(login, password)
+        except CCConf.UnknownAccount:
+            raise AuthenticationError('Authentication failure (Unknown login)')
 
-        role = self._server.conf.authentify(login, password)
         if role is None:
             logging.info('New authentication from %s: failure' % login)
-            return False
+            raise AuthenticationError('Authentication failure')
         else:
             # If authentication is a success, ask tags to the server:
             self._server.register(login, role, connection)