pg_get_constraintdef throws SQL Error [XX000]: ERROR: invalid constraint type "n" (PG17)

Dear support team,

I am writing to report a bug I encountered with the pg_get_constraintdef
function:

CREATE DOMAIN not_null AS TEXT NOT NULL;

CREATE TABLE a (

col not_null

);

SELECT *, pg_get_constraintdef(oid)

FROM pg_constraint

WHERE contype = 'n';

SQL Error [XX000]: ERROR: invalid constraint type "n"

In PG 16 it was ok.
Thank you for your attention to this matter.

Sincerely,
Pierre-Paul