Postgres plpgsql is created by default in new version, but schema dump tries to create it

As of some recent version of Postgres, plpgsql is created for new
databases by default, but the sql schema export
(config.active_record.schema_format = :sql) expots a create command in
development_structure.sql, resulting in an error.

CREATE PROCEDURAL LANGUAGE plpgsql;

I could not find the version this changed in, however it is noted
here:

http://www.postgresql.org/about/featuredetail/feature.185

I believe this is a bug at least in Rails 2.3.5?

My solution was to switch off the sql schema format in environment.rb,
which I don't believe I needed.