Highlighting in search results is case sensitive for cyrillic pattern
When I search any pattern in english everything works fine - highlighting in search results is case insensitive. If I try to search pattern in russian I have case insensitive search output. But highlighting my pattern in that results is case sensitive.
For example if I try to search "ам" pattern it I will see the next:
but 
In source code of search results page this tag <span class="highlight token-0">ам</span> exist for first image and does not exists for the second.
I use MySQL database with utf8_general_ci encoding and apache + passenger on Ubuntu 10.04. Please help me to remove this little issue. Thanks!