Is it possible to at least lock-in a query plan with Postgres? I understand the philosophy behind wanting to keep the queries themselves as declarative as poss

Is it possible to at least lock-in a query plan with Postgres? I understand the philosophy behind wanting to keep the queries themselves as declarative as possible, but there should be some way to prevent a really important query from randomly going rogue and using a stupid index, just because something completely unrelated changed somewhere else in the database.