Description: When trying to do an insert into a table I am receiving:

ERROR: could not load library "/usr/lib/postgresql/plpgsql.so": /usr/lib/postgresql/plpgsql.so: undefined symbol: DatumIsReadWriteExpandedObject

I had originally encountered this in a python program but was able to reproduce it with a simple insert in psql -- e.g.

insert into tasks (details) values ('Hello');

This does NOT happen with updates or selects, only inserts. Upon further testing the problem stems from the table having a trigger which is written in plpgsql.

Downgrading to 9.4.5.1 solves the problem.

Additional info:
* package version(s)
postgresql 9.5.1-1
postgresql-libs 9.5.1-1

* config and/or log files etc.

Steps to reproduce: If you enter the following in psql you will get the error on the last line:

create table t1 (f1 text, d1 timestamp);

create or replace function t1() returns trigger as $$
begin
if TG_OP = 'INSERT' then
NEW.d1 := now();
return NEW;
end if;
end;
$$ language plpgsql;