Wrong checksum calculation in "quickfix.Field.getTotal()"

The "quickfix.Field.getTotal()" method computes the checksum with the following code:
for (int i = 0; i < this.data.length(); ++i)

{ sum += this.data.charAt(i); }

A problem arises if the returned character is written with more than 1 character.
The checksum calculation must be done on "byte"s (the Quickfix specification)

I wrote a correction:
byte[] bytes = null;
try {
bytes = this.data.getBytes(CharsetSupport.getCharset());
for (int i = 0; i < bytes.length; ++i)

{ sum += (((int) bytes[i]) & 0x00FF); }

} catch (UnsupportedEncodingException e)

{ throw new RuntimeException(e); }