Probs with int2 in functions

I'm using PostgreSQL v6.3.2.

It appears that the function command doesn't like the type "int2" as a
parm in a call. For example,

zedadmin=> \i zz.sql
create table test2(
  trk_id        int2            not null,
  trk_nm        varchar(30)     not null,
  trk_comp      varchar(30));
CREATE

create function insert_test2(int2,varchar,varchar)
returns int4 as
 'insert into test2
  values($1,$2,$3);
select 1 as return_val;'
language 'sql';
CREATE
EOF

The objects are successfully created, but when I come to insert data via
the function there is the following error.

zedadmin=> select insert_test2(1,'My name','My comment');
ERROR:  function insert_test2(int4, unknown, unknown) does not exist

If one changes the int2 to an int4 in the table and function, the function
is happy to insert the data into the table.

Any ideas why this is so, or is it a bug?

Cheers...Gordon
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