Using Pspell spellchecker doesn't work for other language than 'en'

[dr-rox]

I am trying to use pspell for spellchecking, but it only works with english language (en). When I select my language, roundcube shows an error "Unable to load Pspell engine for selected language".

In PHP error log, there is PHP Warning:  pspell_new() [function.pspell-new]: PSPELL couldn't open the dictionary. reason: No word lists can be found for the language "lt". in /mail path/program/steps/utils/spell_html_pspell.inc on line 50

My language is lithuanian - lt.

My server has aspell dictionary for lt language, lt appears after writing command "aspell dump dicts". Also spellchecking works when using aspell in console with command "aspell -a -l lt".

I'm running Centos 5.5 with PHP 5.3.3, roundcube config line: $rcmail_config['spellcheck_languages'] = array('en'=>'English', 'lt'=>'Lithuanian');

As I understand, pspell php module uses aspell program to do the work. Or it uses it's own dictionaries? How to configure that to work with my lt dictionary?