regression in PG 15.1

Table is partitioned on a column tbl_id, with an increasing "transaction id".

select * from tbl where txid > something and tbl_id = someval;

^^^ works as normal, searches the single partition, taking 0.044ms

select * from tbl where txid > something and tbl_id = (select id from reftbl where name = 'someval');

^^^ fails to exclude partitions, kicks off parallel scans on all 142, takes 23,170ms

Queries in question are NOT auto-generated from some ORM, so there is an obvious easy workaround. Before trying that, and before digging into full table defs here, does anyone have an idea how to nudge the planner toward excluding the partitions.

--
Scott Ribe
scott_ribe(at)elevated-dev(dot)com
https://www.linkedin.com/in/scottribe/