"deprecated" error message in apache error log

I am seeing the "warning: Object#id will be deprecated; use
Object#object_id" message coming from ActionController in my apache
error log. I do not see it anywhere else -- neither the production nor
development rails logs.

Something is calling dom_id with something that is not an active record
I guess. How can I track down who is doing this?

I'm running Rails 2.1.