Updating a chkpass column in postgres v8.1.21

I am using the JDBC prepareStatement object to build a SQL statement that should update a users password in a postgres v8.1.21 database. (Based on what I have read, chkpass became a "contrib module" starting at 8.3, but I have to use an older version of postgres.) Here is my java code/snippet:

// Build an SQL statement with caller's parameters
private static final String m_defaultPass = "changeme";
stmtStr = "UPDATE users SET pwd_date=now(), pwd=? " + "WHERE user_id=?;";
stmt = con.prepareStatement(stmtStr);
stmt.setString(1, m_defaultPass);
stmt.setString(2, userId);

(userId is a String that is passed into the method)

The password column in the database is defined as type chkpass.
userdb=# \d users
Table "public.users"
Column | Type | Modifiers
-------------------+-----------------------------+-------------------------------------------------------------------
user_pk | integer | not null default nextval(('"users_user_pk_seq"'::text)::regclass)
user_id | character varying(10) | not null
pwd | chkpass | not null
:

chkpass is a user created type, and is defined as follows:
CREATE TYPE chkpass (
INTERNALLENGTH = 16,
INPUT = chkpass_in,
OUTPUT = chkpass_out,
ALIGNMENT = int4,
STORAGE = plain
);

When the above java snippet is executed, I get the following error:
column "pwd" is of type chkpass but expression is of type character varying.

How do I modify my SQL statement to get this to work properly?

Thanks in advance!
Howard