diff --git a/openerp/osv/orm.py b/openerp/osv/orm.py
index 86ce76cb6f9..76b4d7ee3ff 100644
--- a/openerp/osv/orm.py
+++ b/openerp/osv/orm.py
@@ -1562,12 +1562,9 @@ class BaseModel(object):
                 # Check presence of __call__ directly instead of using
                 # callable() because it will be deprecated as of Python 3.0
                 if hasattr(msg, '__call__'):
-                    tmp_msg = msg(self, cr, uid, ids, context=context)
-                    if isinstance(tmp_msg, tuple):
-                        tmp_msg, params = tmp_msg
-                        translated_msg = tmp_msg % params
-                    else:
-                        translated_msg = tmp_msg
+                    translated_msg = msg(self, cr, uid, ids, context=context)
+                    if isinstance(translated_msg, tuple):
+                        translated_msg = translated_msg[0] % translated_msg[1]
                 else:
                     translated_msg = trans._get_source(cr, uid, self._name, 'constraint', lng, msg)
                 if extra_error: