missing FROM-clause entry

Just upgraded to 8.1.5 and the following UPDATE causes the "missing
FROM-clause entry" error:

  UPDATE model_timemap
      SET map = updatemap( CASE WHEN replica = 32188 THEN 328787 WHEN replica = 32191 THEN 5739 ELSE -1 END,
1161642129,map) 
      WHERE replica.replica_id = model_timemap.replica AND replica.proxy = 32189

From what I've read, this typically results from referring to a table
instead of it's alias, but I don't see how that applies here.

--
Brandon