EXCEPT doesn't compare TIMESTAMP type?

Hi, could anyone please tell me what is wrong in below query. Does it mean
that EXCEPT doesn't allow comparing TIMESTAMP type?

techdb=# INSERT INTO changelogtest (id, txid, txtime) values (5, 123, 'now')
except select id, txid, txtime
from changelogtest
where id=5;
ERROR: EXCEPT types text and timestamp without time zone cannot be matched
LINE 2: except select id, txid, txtime
^

Thanks,
Dipti