QSqlTableModel.submitAll() problems with milliseconds and PostgreSQL time field

If I create a PostgreSQL database 'test' and execute the following:
CREATE TABLE timetest ( t time );
INSERT INTO timetest VALUES ('0:0:0');

then run the attached test program (derived from qt demo) the output is:

Model value: "00:00:00.000"
Post setData: "00:12:34.500"
Post submitAll: "00:12:34.000"

The database doesn't get the 500 milliseconds.

Even worse if I execute on the database:
UPDATE timetest SET t = '0:11:22.33';

and run the test program:
Model value: "00:11:22.330"
Post setData: "00:12:34.500"
Post submitAll: "00:11:22.330"

the value from the model doesn't make it into the database at all if the
time field already has milliseconds.

Linux amd64, postgresql-8.4.1