Modifying http response on iRule corrupts scandinavian characters, how to prevent?

So far all the articles which mention using stream profile basically instruct to active stream profile on virtual server and have an iRule for the actual content manipulation.

Is there some other way or something wrong with our approach?

Our current stream modification rule looks something like this:

when HTTP_REQUEST {
    STREAM::disable
    HTTP::header remove "Accept-Encoding"
    set targethost [string tolower [HTTP::host]]
}
when HTTP_RESPONSE {
    switch  $targethost {
        publish.mycompany.com {
            set wronghost "https://www2.mycompany.com"
            set correcthost "https://publish.mycompany.com"
        }
        ...
    }

    if {[HTTP::header value Content-Type] contains "text"}{
        STREAM::expression "@$wronghost@$correcthost@"
        STREAM::enable
    }
}