Problem with stored procedure

Hello,

In this example, I use 2 tables :
create table types (
typnum integer primary key,
catcode varchar(2),
typlib varchar(35));

create table uv (
uvnum varchar(5) primary key,
typnum integer,
uvlib varchar(50));

alter table uv
add constraint fk_uv_type foreign key (typnum)
references types (typnum)
on delete restrict on update restrict;

I also use stored procedures :

create function numtype(varchar) returns integer as '
declare
codetype alias for $1;
coderet integer;
begin
select into coderet typnum from types
where typcode = codetype and catcode = ''UV'';
return coderet;
end;
' language 'plpgsql';

create function insert_uv(varchar,varchar,varchar) returns integer as '
declare
codeuv alias for $1;
codetype alias for $2;
libuv alias for $3;
cletype integer;
begin
select into cletype numtype(codeuv);
insert into uv values (codeuv, cletype, libuv);
return cletype;
end;
' language 'plpgsql';

When I do :

select insert_uv('SGBD','DUVC','TEST BD');
I get the following message :
ERROR: insert or update on table "uv" violates foreign key constraint
"fk_uv_caracteri_type"
DETAIL: Key (typnum)=(43) is not present in table "types".

I don't kown why.

Anyone has an idea ?

With best regards,
Patrice