[Cross-posted from the OAuth Ruby Google Group. If you couldn't help me there, don't worry bout it] I'm working on integrating a project with TripIt's OAuth API and am running into a weird issue. I authenticate fine, I store and retrieve the token/secret for a given user with no problem, I can even make GET requests to a number of services using the gem. But when I try using the one service I need POST for, I'm getting a 401 "invalid signature" response. Perhaps I'm not understanding how to pass in data to the AccessToken's post method, so here's a sample of my code: xml = <<-XML <Request> <Trip> <start_date>2008-12-09</start_date> <end_date>2008-12-27</end_date> <primary_location>New York, NY</primary_location> </Trip> </Request> XML` response = access_token.post('/v1/create', {:xml => xml}, {'Content-Type' => 'application/x-www-form-urlencoded'}) I've tried this with and without escaping the xml string before hand. The guys at TripIt seemed to think that perhaps the xml param wasn't getting included in the signature_base_string, but when I output that (from lib/signature/base.rb) I see: POST&https%3A%2F%2Fapi.tripit.com%2Fv1%2Fcreate&oauth_consumer_key %3D%26oauth_nonce %3Djs73Y9caeuffpmPVc6lqxhlFN3Qpj7OhLcfBTYv8Ww%26oauth_signature_method %3DHMAC-SHA1%26oauth_timestamp%3D1252011612%26oauth_token %3D%26oauth_version%3D1.0%26xml%3D%25253CRequest%25253E %25250A%252520%252520%25253CTrip%25253E%25250A %252520%252520%252520%252520%25253Cstart_date%25253E2008-12-09%25253C %252Fstart_date%25253E%25250A %252520%252520%252520%252520%25253Cend_date%25253E2008-12-27%25253C %252Fend_date%25253E%25250A %252520%252520%252520%252520%25253Cprimary_location%25253ENew %252520York%252C%252520NY%25253C%252Fprimary_location%25253E%25250A %252520%252520%25253C%252FTrip%25253E%25250A%25253C%252FRequest%25253E %25250A This seems to be correct to me. I output signature (from the same file) and the output doesn't match the oauth_signature param of the Auth header in lib/client/ net_http.rb. It's been URL-encoded in the auth header. Is this correct? Anyone know if the gem is broken/if there's a fix somewhere? I'm finding it hard to trace through some of the code.