Ruby-1.9: "binary" fields are represented by string whose encoding is "UTF-8"

When reading a thrift object using the Thrift::BinaryProtocol and this thrift object has a field of type "binary", then accessing this field yields a string whose encoding is "UTF-8".
The encoding should be "ASCII-8BIT" instead. It may be right to assume that "string" fields have a character encoding (such as "UTF-8"), but "binary" fields do not have a character encoding at all. For these cases, there is the pseudo-encoding "ASCII-8BIT" where we deal just with an opaque sequence of bytes.