partial index on varchar-coloumn in 7.4.1

Hi,

I am trying to use an partial index on a varchar-coloumn as described
in the documentation (section 11.7.)

The commands I ran were:

CREATE INDEX word_idx on token (word) where not (word = 'the');
ANALYZE;

The problem is: PostgreSQL doesn't seem to use this index at all. It
does use it if I create the index for the whole table.

Do partial indexes not work for varchar? Or do I have a syntax error in
my command?

Thanks,
Martin.