Gmail does not detect the reply-to field

I have following settings in my FeedbackMailer.

def notification(feedback)

  from       "admin@gmail.com"
  subject    "Some feedback"
  recipients "admin@gmail.com"
  reply_to   feedback.creator.email
  body({ :feedback => feedback })
  content_type "text/html"
end

I am using admin@gmail.com account to send emails for this application. The emails are delivered perfectly. And when I check the details of the email after receiving it, I see following:

from     "admin@gmail.com"
reply-to "user_email@foo.com"
to       "admin@gmail.com"

Now when I press on the reply button in the gmail interface, the to field should now have the "user_email@foo.com" but it is having "admin@gmail.com". Am I doing something wrong or gmail is?