diff --git a/tryton/rpc.py b/tryton/rpc.py
index 96c3aba5fe..892222c695 100644
--- a/tryton/rpc.py
+++ b/tryton/rpc.py
@@ -9,7 +9,7 @@ from tryton.fingerprints import Fingerprints
 from tryton.config import get_config_dir
 
 _SOCK = None
-_USER = 0
+_USER = None
 _USERNAME = ''
 _SESSION = ''
 _DATABASE = ''
@@ -141,11 +141,11 @@ def login(username, password, host, port, database):
             _SOCK.reconnect()
         except (socket.error, RuntimeError):
             pass
-        _USER = 0
+        _USER = None
         _SESSION = ''
         return -1
     if not res:
-        _USER = 0
+        _USER = None
         _SESSION = ''
         return -2
     _USER = res[0]
@@ -174,7 +174,7 @@ def logout():
             pass
         _SOCK.disconnect()
         _SOCK = None
-    _USER = 0
+    _USER = None
     _USERNAME = ''
     _SESSION = ''
     _DATABASE = ''