pg_rewind restore_command issue in PG12

   Hi;

     In a situation where pg_rewind gets an error due to a missing wall, I  have set restore_command so that the needed wals can be read from the archive (I don't want to manually copy the wal files), but I see it doesn't work. What am I missing?  Is restore_command not really working with pg_rewind in PG12? Or  how should I trigger pg_rewind to use restore_command?

Thank you.