POST parameters incorrectly appended to REQUEST_URI

My rspec controller tests are appending POST params to the request_uri
as though they are GET variables.

So this line:

post :create, :foo => 'bar'

Generates a request_uri that looks like this:

my_restful_controller?foo=bar

However when performing the same action from the actual application, the
params are not appended to the request_uri (as expected).

Looks like this issue has been raised elsewhere, and by the sounds of
it, this is an issue with rails functional tests.

http://rubyforge.org/tracker/?func=detail&atid=3149&aid=15282&group_id=797

Yet I haven't found a solution / workaround to the problem. Has anyone
else experienced issues with this?