hpricot：Hpricot::Elements#remove_class

>> require "hpricot"
=> true
>> doc = Hpricot('<p class="hoge1">foo1</p><p class="hoge2">foo2</p>')
=> #<Hpricot::Doc {elem <p class="hoge1"> "foo1" </p>} {elem <p class="hoge2"> "foo2" </p>}>
>> (doc / "p").remove_class("hoge1")
=> #<Hpricot::Elements[{elem <p class=""> "foo1" </p>}, {elem <p class="hoge2"> "foo2" </p>}]>
>> doc.to_html
=> "<p class=\"\">foo1</p><p class=\"hoge2\">foo2</p>"
>> (doc / "p").remove_class
=> #<Hpricot::Elements[{elem <p> "foo1" </p>}, {elem <p> "foo2" </p>}]>

名前を指定した場合には class 自体が消えない仕様なの？