Multibyte character corrupt in highlight method


When I apply highlight() method to the search result,
multibyte characters are corrupted.
The post_tag is located in the middle of last character,
so the last character corrupts.

Here is my code.

searcher.search_each(query) do |doc_id, score|
puts searcher.highlight(query, doc_id, :field => :content)

And this is the result.

… bla, bla, bla, … SOME_MULTIBYTE_CHARACTERS …

How can I do??