Dropping functions with missing argument types

[I didn't find any related info on techdocs.postgresql.org or on the
mailing list archives.]

I goofed up our demo database, and had to restore it from a backup
made by pg_backup.sh (which uses pg_dump in "custom" binary mode).

After restoring the demo database, I tried dumping it again to see
if there were any residual issues from the restore. I got the
following errors (after restoring the named functions):

$ pg_dump -S postgres demodb > demodb.out
Notice: function "get_sort_name" is not dumped.
Reason: the 0 th argument type name (oid 1388921) not found.
Notice: function "get_sort_name" is not dumped.
Reason: the 0 th argument type name (oid 1389578) not found.
Notice: function "get_name" is not dumped.
Reason: the 0 th argument type name (oid 1388744) not found.
Notice: function "get_name" is not dumped.
Reason: the 0 th argument type name (oid 1388921) not found.
Notice: function "get_name" is not dumped.
Reason: the 0 th argument type name (oid 1389578) not found.
$ psql demodb demouser

demodb=> \df get_sort_name
List of functions
Result | Function | Arguments
-------------------+---------------+-------------
character varying | get_sort_name | ???
character varying | get_sort_name | ???
character varying | get_sort_name | table1
character varying | get_sort_name | table2
(4 rows)

demodb=> \df get_name
List of functions
Result | Function | Arguments
-------------------+----------+-------------
character varying | get_name | ???
character varying | get_name | ???
character varying | get_name | ???
character varying | get_name | table3
character varying | get_name | table1
character varying | get_name | table2
(6 rows)

demodb=> \q

I don't believe I will be able to delete these errant functions using
the standard DROP FUNCTION command.

What is the best way to delete them? Am I able to simply identify and
delete the corresponding rows from the PG_PROC table? Are there any
other system tables that I need to update if I delete rows from the
PG_PROC table?

Thanks!

Dave