Confused about case-sensitivity

I have two fields in a xappy index, both using INDEX_FREETEXT, one
having a "language" option applied, the other not.

The stemmed fields work as expected, case does not matter at all.

The unstemmed fields mostly seem to ignore case as well - except for
the first character:

For example, the term "gee" in that field will be matched by "GEE",
"GeE" etc., but not by "gee" or "geE". Even more strange, the case of
the term I originally indexed doesn't seem to matter either. If the
term is "buffed", I have to query for "Buffed" to find the document.

Any idea what might be wrong here? If not, any suggestions on how to
debug this?

Using SVN checkout, xapian retrieved via libs\get_xapian.py, Windows