BUG #14327: UPSERT requires full path to column

The following bug has been logged on the website:

Bug reference: 14327
Logged by: Egor Pugin
Email address: egor(dot)pugin(at)gmail(dot)com
PostgreSQL version: 9.5.4
Operating system: win10
Description:

Hi,

I've noticed upsert query won't work if I do not write 'schema.TABLE.column'
instead of simple 'column' in 'on conflict do update set' query.

Working:

insert into statistics."MostPopularDependencies"
(id, indirect, downloads_week)
values ($1, $2, 1)
on conflict (id, indirect) do update
set downloads_week = statistics."MostPopularDependencies".downloads_week +
1
where statistics."MostPopularDependencies".id = $1 and
statistics."MostPopularDependencies".indirect = $2;

Not working:

insert into statistics."MostPopularDependencies"
(id, indirect, downloads_week)
values ($1, $2, 1)
on conflict
(id, indirect) -- also w/out this, it does not work too, but isn't it
optional element?
do update
set downloads_week = downloads_week + 1
where id = $1 and indirect = $2;