Changes to error handling for background worker initialization?

Hello -

I have an extension that uses background workers. I pass a database oid as
an argument in order to launch the worker using function
BackgroundWorkerInitializeConnectionByOid. In one of my regression tests
that was written, I intentionally launch the worker with an invalid oid.
In earlier PG versions the worker would successfully launch but then
terminate asynchronously, with a message in the server log. Now, it does
not even successfully launch but immediately errors (hence failing my
regression tests).

I have recently installed all later point releases of all versions 9.5-11,
so I assume this is due to some code change. The behavior seems reasonable
but I don't find any obvious release notes indicating a patch that would
have changed this behavior. Any thoughts?

Thanks,
Jeremy