Issue with postgres 11beta2 and powa on debian stretch amd64

Hello,

I installed postgresql-11-powa on a fresh debian stretch amd64 with
postgresql-11 beta2

I got several errors "set-valued function called in context that cannot accept a
set" which should be fixed :
2018-07-22 14:16:22.209 CEST [30135] WARNING: powa_take_snapshot(): function
"powa_user_functions_snapshot" failed:
state : 0A000
message: set-valued function called in context that cannot
accept a set
detail :
hint :
context: SQL statement "WITH func(dbid, r) AS (
SELECT oid,
powa_stat_user_functions(oid)
FROM pg_database
)
INSERT INTO powa_user_functions_history_current
SELECT dbid, (r).funcid,
ROW(now(), (r).calls,
(r).total_time,
(r).self_time)::powa_user_functions_history_record AS record
FROM func"
PL/pgSQL function powa_user_functions_snapshot() line 10 at SQL statement
SQL statement "SELECT powa_user_functions_snapshot()"
PL/pgSQL function powa_take_snapshot() line 76 at EXECUTE
SQL statement "SELECT powa_take_snapshot()"

FYI, I do not have this error if I build powa from github's sources. So, I seems
it is a packing issue.

Thanks

--
Adrien NAYRAT