diff --git a/example/Dropbox/test.hs b/example/Dropbox/test.hs
new file mode 100644
--- /dev/null
+++ b/example/Dropbox/test.hs
@@ -0,0 +1,39 @@
+{-# LANGUAGE FlexibleContexts  #-}
+{-# LANGUAGE OverloadedStrings #-}
+{-# LANGUAGE TemplateHaskell   #-}
+
+module Main where
+
+import           Control.Monad                 (liftM)
+import           Data.Aeson.TH         (defaultOptions, deriveJSON)
+import qualified Network.HTTP.Types            as HT
+import qualified Data.ByteString.Char8 as BS
+import qualified Data.ByteString.Lazy.Char8    as BSL
+import qualified Data.Text             as T
+import qualified Data.Text.Encoding    as T
+import           Network.HTTP.Conduit
+
+import           Network.OAuth.OAuth2
+
+import           Keys
+
+
+main :: IO ()
+main = do
+    print $ authorizationUrl dropboxKey
+    putStrLn "visit the url and paste code here: "
+    code <- fmap BS.pack getLine
+    mgr <- newManager tlsManagerSettings
+    token <- fetchAccessToken mgr dropboxKey code
+    print token
+    case token of
+      Right at  -> getSpaceUsage mgr at >>= print
+      Left _    -> putStrLn "no access token found yet"
+
+getSpaceUsage :: Manager -> AccessToken -> IO (OAuth2Result BSL.ByteString)
+getSpaceUsage mgr token = do
+  req <- parseRequest $ BS.unpack "https://api.dropboxapi.com/2/users/get_space_usage"
+  authRequest req upReq mgr
+  where upHeaders = updateRequestHeaders (Just token) . setMethod HT.POST
+        upBody req = req {requestBody = "null" }
+        upReq = upHeaders . upBody
diff --git a/example/Keys.hs.sample b/example/Keys.hs.sample
--- a/example/Keys.hs.sample
+++ b/example/Keys.hs.sample
@@ -61,3 +61,10 @@
                           , oauthOAuthorizeEndpoint = "https://stackexchange.com/oauth"
                           , oauthAccessTokenEndpoint = "https://stackexchange.com/oauth/access_token"
                           }
+dropboxKey :: OAuth2
+dropboxKey = OAuth2 { oauthClientId = "xxx"
+                    , oauthClientSecret = "xxx"
+                    , oauthCallback = Just "http://localhost:9988/oauth2/callback"
+                    , oauthOAuthorizeEndpoint = "https://www.dropbox.com/1/oauth2/authorize"
+                    , oauthAccessTokenEndpoint = "https://api.dropboxapi.com/oauth2/token"
+                    }
diff --git a/hoauth2.cabal b/hoauth2.cabal
--- a/hoauth2.cabal
+++ b/hoauth2.cabal
@@ -1,6 +1,6 @@
 Name:                hoauth2
 -- http://wiki.haskell.org/Package_versioning_policy
-Version:             0.5.6.0
+Version:             0.5.7
 
 Synopsis:            Haskell OAuth2 authentication client
 Description:
@@ -237,3 +237,27 @@
                    -fno-warn-unused-do-bind
   else
       ghc-options: -Wall -fwarn-tabs -funbox-strict-fields
+
+Executable test-dropbox
+  if flag(test)
+    Buildable: True
+  else
+    Buildable: False
+
+  main-is:             Dropbox/test.hs
+  hs-source-dirs:      example
+  default-language:    Haskell2010
+  build-depends:       base              >= 4.5    && < 5,
+                       http-types        >= 0.9    && < 0.10,
+                       http-conduit      >= 2.2    && < 2.3,
+                       text              >= 0.11   && < 1.3,
+                       bytestring        >= 0.9    && < 0.11,
+                       aeson             >= 1.0    && < 1.1,
+                       hoauth2
+
+  if impl(ghc >= 6.12.0)
+      ghc-options: -Wall -fwarn-tabs -funbox-strict-fields
+                   -fno-warn-unused-do-bind
+  else
+      ghc-options: -Wall -fwarn-tabs -funbox-strict-fields
+
diff --git a/src/Network/OAuth/OAuth2/HttpClient.hs b/src/Network/OAuth/OAuth2/HttpClient.hs
--- a/src/Network/OAuth/OAuth2/HttpClient.hs
+++ b/src/Network/OAuth/OAuth2/HttpClient.hs
@@ -16,6 +16,7 @@
   authGetBS',
   authPostJSON,
   authPostBS,
+  authPostBS',
   authRequest,
 -- * Utilities
   handleResponse,
@@ -144,6 +145,19 @@
         upHeaders = updateRequestHeaders (Just token) . setMethod HT.POST
         upReq = upHeaders . upBody
 
+-- | Conduct POST request with access token in the request body rather header
+authPostBS' :: Manager                             -- ^ HTTP connection manager.
+             -> AccessToken
+             -> URI                               -- ^ URL
+             -> PostBody
+             -> IO (OAuth2Result BSL.ByteString)  -- ^ Response as ByteString
+authPostBS' manager token url pb = do
+  req <- parseUrl $ BS.unpack url
+  authRequest req upReq manager
+  where upBody = urlEncodedBody (pb ++ accessTokenToParam token)
+        upHeaders = updateRequestHeaders Nothing . setMethod HT.POST
+        upReq = upHeaders . upBody
+
 -- |Send an HTTP request including the Authorization header with the specified
 --  access token.
 --
@@ -162,7 +176,7 @@
 handleResponse rsp =
     if HT.statusIsSuccessful (responseStatus rsp)
         then Right $ responseBody rsp
-        else Left $ BSL.append "hoauth2.HttpClient.parseResponseJSON/Gaining token failed: " (responseBody rsp)
+        else Left $ BSL.append "hoauth2.HttpClient.handleResponse/Gaining token failed: " (responseBody rsp)
 
 -- | Parses a @OAuth2Result BSL.ByteString@ into @FromJSON a => a@
 parseResponseJSON :: FromJSON a
@@ -186,7 +200,7 @@
   where
     queryToValue = Object . HM.fromList . map paramToPair
     paramToPair (k, mv) = (T.decodeUtf8 k, maybe Null (String . T.decodeUtf8) mv)
-    errorMessage = ("hoauth2.HttpClient.parseResponseJSON/Could not decode JSON or URL: " `BSL.append` b)
+    errorMessage = "hoauth2.HttpClient.parseResponseJSON/Could not decode JSON or URL: " `BSL.append` b
 
 -- | Try 'parseResponseJSON' and 'parseResponseString'
 parseResponseFlexible :: FromJSON a
diff --git a/src/Network/OAuth/OAuth2/Internal.hs b/src/Network/OAuth/OAuth2/Internal.hs
--- a/src/Network/OAuth/OAuth2/Internal.hs
+++ b/src/Network/OAuth/OAuth2/Internal.hs
@@ -96,11 +96,10 @@
                     -> (URI, PostBody)        -- ^ access token request URL plus the request body.
 accessTokenUrl' oa code gt = (uri, body)
   where uri  = oauthAccessTokenEndpoint oa
-        body = transform' [ ("client_id", Just $ oauthClientId oa)
-                          , ("client_secret", Just $ oauthClientSecret oa)
-                          , ("code", Just code)
+        body = transform' [ ("code", Just code)
                           , ("redirect_uri", oauthCallback oa)
-                          , ("grant_type", gt) ]
+                          , ("grant_type", gt)
+                          ]
 
 -- | Using a Refresh Token.  Obtain a new access token by
 -- sending a refresh token to the Authorization server.
@@ -109,10 +108,9 @@
                          -> (URI, PostBody)  -- ^ refresh token request URL plus the request body.
 refreshAccessTokenUrl oa rtoken = (uri, body)
   where uri = oauthAccessTokenEndpoint oa
-        body = transform' [ ("client_id", Just $ oauthClientId oa)
-                          , ("client_secret", Just $ oauthClientSecret oa)
-                          , ("grant_type", Just "refresh_token")
-                          , ("refresh_token", Just rtoken) ]
+        body = transform' [ ("grant_type", Just "refresh_token")
+                          , ("refresh_token", Just rtoken)
+                          ]
 
 --------------------------------------------------
 -- * UTILs