diff --git a/addons/web/common/dispatch.py b/addons/web/common/dispatch.py
index dbd9e3ac71f..afcde2edfad 100644
--- a/addons/web/common/dispatch.py
+++ b/addons/web/common/dispatch.py
@@ -23,6 +23,7 @@ import nonliterals
 import http
 # import backendlocal as backend
 import session as backend
+import openerplib
 
 __all__ = ['Root', 'jsonrequest', 'httprequest', 'Controller',
            'WebRequest', 'JsonRequest', 'HttpRequest']
@@ -166,7 +167,7 @@ class JsonRequest(WebRequest):
                 _logger.debug("--> %s.%s\n%s", controller.__class__.__name__, method.__name__, pprint.pformat(self.jsonrequest))
             response['id'] = self.jsonrequest.get('id')
             response["result"] = method(controller, self, **self.params)
-        except backend.OpenERPUnboundException:
+        except openerplib.AuthentificationError:
             error = {
                 'code': 100,
                 'message': "OpenERP Session Invalid",
diff --git a/addons/web/common/session.py b/addons/web/common/session.py
index cdedf7962da..3691f88e3f5 100644
--- a/addons/web/common/session.py
+++ b/addons/web/common/session.py
@@ -8,8 +8,6 @@ import nonliterals
 #----------------------------------------------------------
 # OpenERPSession RPC openerp backend access
 #----------------------------------------------------------
-class OpenERPUnboundException(Exception):
-    pass
 
 class OpenERPSession(object):
     """
@@ -68,8 +66,7 @@ class OpenERPSession(object):
         """
         Ensures this session is valid (logged into the openerp server)
         """
-        if not (self._db and self._uid and self._password):
-            raise OpenERPUnboundException()
+        self.build_connection().check_login(False)
 
     def execute(self, model, func, *l, **d):
         self.assert_valid()