Email Sending Now Throws Error in 2.0.2

(sorry if this is a dupe - first one didn't go through)

This code worked fine in 1.1.6. I just migrated to 2.0.2 and I get the
error below. However, the fix that is suggested in the error does not apply
to my code. I don't use an explicit call to "render." Furthermore, the
latest API documentation for ActionMailer doesn't mention explicitly calling
"render." This is driving me nuts! Any help? Thanks!

# code

#In my Controller

  def create
    ...
      MembershipRequestMailer.deliver_receipt(@membership_request)
    ...
  end

# In my Mailer

class MembershipRequestMailer < ActionMailer::Base

  def receipt(membership_request)
    @subject = 'NASDCTEc Membership Request Submission'
    @recipients = membership_request.email
    @from = 'do-not-reply@foo.org'
    @sent_on = Time.now
    @body["membership_request"] = membership_request
    @content_type = "text/html"
  end

  def submission(membership_request)
    @subject = 'Membership Request Submission'
    @recipients = 'foo@gmail.com'
    @from = 'do-not-reply@foo.org'
    @sent_on = Time.now
    @body["membership_request"] = membership_request
    @content_type = "text/html"
  end

end

# error

Due to changes in ActionMailer, you need to provide the mailer_name along
with the template name.

  render "user_mailer/signup"
  render :file => "user_mailer/signup"

If you are rendering a subtemplate, you must now use controller-like partial
syntax:

  render :partial => 'signup' # no mailer_name necessary