Problem with lower() for unicode strings in russian

[Alexey Moskvin]

Hi!
I have a set of strings (all letters are capitalized) at utf-8,
russian language. I need to lower it, but
my_string.lower(). Doesn't work.
See sample script:
# -*- coding: utf-8 -*-
[skip]
s1 = self.title
s2 = self.title.lower()
print s1 == s2

returns true.
I have no problems with lower() for english letters:, or with
something like this:
u'russian_letters_here'.lower(), but I don't need constants, I need to
modify variables, but there is no any changs, when I apply lower()
function to mine strings.