The header is omitted here (returns empty list)
Unirest.get("https://google.de/").header("Accept-Encoding", "gzip").asString().headers.get("Content-Encoding")

The following prints nothing (header also omitted)

Unirest.get("https://google.de/").header("Accept-Encoding", "gzip").thenConsume {
    println(it.encoding)
}