Bug in sequence dependency checking

Hello all,

PostgreSQL do not remove it's internal dependency when I DROP DEFAULT (it was nextval(...)),
so I still can't remove the sequence. Please see the real example bellow:

isbs=# \d ttPrefixes
Table "public.ttprefixes"
Column | Type | Modifiers
--------+---------+---------------------------------------------------------------
ttpid | integer | not null default nextval('public.ttprefixes_ttpid_seq'::text)
ttid | integer | not null default nextval('public.ttprefixes_ttid_seq'::text)
prefix | text |
descr | text |
dton | date |
dtoff | date |
Indexes: ttprefixes_pkey primary key btree (ttpid)
Foreign Key constraints: $1 FOREIGN KEY (ttid) REFERENCES teltypes(ttid) ON UPDATE NO ACTION ON DELETE
CASCADE

isbs=# alter table ttPrefixes alter ttid DROP DEFAULT;
ALTER TABLE

isbs=# \d ttPrefixes
Table "public.ttprefixes"
Column | Type | Modifiers
--------+---------+---------------------------------------------------------------
ttpid | integer | not null default nextval('public.ttprefixes_ttpid_seq'::text)
ttid | integer | not null
prefix | text |
descr | text |
dton | date |
dtoff | date |
Indexes: ttprefixes_pkey primary key btree (ttpid)
Foreign Key constraints: $1 FOREIGN KEY (ttid) REFERENCES teltypes(ttid) ON UPDATE NO ACTION ON DELETE
CASCADE

isbs=# DROP sequence public.ttprefixes_ttpid_seq;
ERROR: Cannot drop sequence ttprefixes_ttpid_seq because table ttprefixes column ttpid requires it
You may drop table ttprefixes column ttpid instead

isbs=# select version();
version
---------------------------------------------------------------------
PostgreSQL 7.3.2 on i386-unknown-freebsd4.7, compiled by GCC 2.95.4
(1 row)

See last DROP command - it's not executed, but the ttprefixes table don't really "require" the sequence -
I had dropped the DEFAULT! Is it possible to force deletion of such sequences ? Thanks for advance.

--
best regards,
Ruslan A Dautkhanov rusland(at)scn(dot)ru