BUG #12292: index row size 1480 exceeds maximum 1352 for index

The following bug has been logged on the website:

Bug reference: 12292
Logged by: robert thaler
Email address: robert(dot)thaler(at)cellent(dot)at
PostgreSQL version: 9.4.0
Operating system: linux ubuntu 14.04.1 LTS x86_64
Description:

I tried to upgrade from postgres 9.3.5 and imported a database export
created by pg_dump. the import shows the following error:
ERROR: index row size 1480 exceeds
maximum 1352 for index "idx_sm_post_content"

manually creating the gin index for fulltext search does not work too and
produces the same error.

create index idx_sm_post_content
on client.sm_post using gin (to_tsvector('english', "content"))

on postgres 9.3.5 creating the index on the same data works fine.

kind regards