tsearch prefix searching doesn't work when last char of prefix is accent char

Hello

I found a following bug

create table n(a varchar);
postgres=# insert into n values('Stěhule'),('Chromečka');

postgres=# select * from n;
a
───────────
Stěhule
Chromečka
(2 rows)

-- work
postgres=# select * from n where to_tsvector('cs', a) @@
to_tsquery('cs','St:*') ;
a
─────────
Stěhule
(1 row)

-- doesn't work
postgres=# select * from n where to_tsvector('cs', a) @@
to_tsquery('cs','Stě:*') ;
a
───
(0 rows)

-- work again
postgres=# select * from n where to_tsvector('cs', a) @@
to_tsquery('cs','Stěh:*') ;
a
─────────
Stěhule
(1 row)

postgres=# select version();
version
──────────────────────────────────────────────────────────────────────────────────────────────────────────
PostgreSQL 9.2devel on i686-pc-linux-gnu, compiled by gcc (GCC) 4.5.1
20100924 (Red Hat 4.5.1-4), 32-bit
(1 row)

postgres=# show server_encoding;
server_encoding
─────────────────
UTF8
(1 row)

postgres=# show lc_collate ;
lc_collate
─────────────
cs_CZ.utf-8
(1 row)

Regards

Pavel Stehule