[Pymilter] milter.error: cannot add header

[Andrew Azarov]

Traceback (most recent call last):
  File "/usr/local/lib/python2.5/site-packages/Milter/__init__.py", line 
203, in <lambda>
    milter.set_eom_callback(lambda ctx: ctx.getpriv().eom())
  File "./avlmilter", line 259, in eom
    self.addheader("X-AVLMail-Status", "Passed")
  File "/usr/local/lib/python2.5/site-packages/Milter/__init__.py", line 
110, in addheader
    return self.__ctx.addheader(field,value,idx)
milter.error: cannot add header

Where can it come from?