Problem in searching with multibyte character

The following message always shows when I use even 2 multibyte characters as searching criteria.

The following words in your search query were ignored: 孔雀 .
You must specify at least one word to search for. Each word must consist of at least 4 characters and must not contain more than 84 characters excluding wildcards.

I'm using Fulltext mysql as search backend with "Support for non-latin UTF-8 characters using PCRE" (PHP 5.2.3)