Problem with rake db:test prepare in RoR-3.1.1 and PostgreSQl-9.1?

ruby-1.8.7-p352 [ x86_64 ]

When I do this:
$ rake db:test:prepare
Using AdapterExtensions

Then I see this:

psql:/…/db/development_structure.sql:22: ERROR: must be owner of
extension plpgsql

The offending line is

22 COMMENT ON EXTENSION plpgsql IS ‘PL/pgSQL procedural language’;

Which, to me, is simply noise. I have never seen this problem before
but I am now running tests against PostgreSQl-9.1 whereas before we
were using 8.4.x. Has anyone else seen this? Is there a fix? Google
does not turn up anything that strikes me as being relevant.