error

ERROR:tryton.common.common:Traceback (most recent call last):
  File "/trytond/protocols/jsonrpc.py", line 123, in _marshaled_dispatch
    response['result'] = dispatch_method(method, params)
  File "/trytond/protocols/jsonrpc.py", line 156, in _dispatch
    res = dispatch(*args)
  File "/trytond/protocols/dispatcher.py", line 158, in dispatch
    result = rpc.result(meth(*args, **kwargs))
  File "/trytond/model/model.py", line 332, in default_get
    value = cls._default_on_change(value)
  File "/trytond/model/model.py", line 358, in _default_on_change
    val2.update(Target._default_on_change(val2))
AttributeError: 'int' object has no attribute 'update'