diff --git a/Network/AWS/Authentication.hs b/Network/AWS/Authentication.hs
--- a/Network/AWS/Authentication.hs
+++ b/Network/AWS/Authentication.hs
@@ -101,9 +101,10 @@
                     . s3metadata
 
 -- | Inspect HTTP body, and add a @Content-Length@ header with the
---   correct length.
+--   correct length, if it does not already exist.
 addContentLengthHeader :: HTTP.HTTPRequest L.ByteString -> HTTP.HTTPRequest L.ByteString
-addContentLengthHeader req = insertHeader HdrContentLength (show (L.length (rqBody req))) req
+addContentLengthHeader req = insertHeaderIfMissing HdrContentLength conlength req
+    where conlength = show (L.length (rqBody req))
 
 -- | Add AWS authentication header to an HTTP request.
 addAuthenticationHeader :: S3Action     -- ^ Action with authentication data
diff --git a/Network/AWS/S3Object.hs b/Network/AWS/S3Object.hs
--- a/Network/AWS/S3Object.hs
+++ b/Network/AWS/S3Object.hs
@@ -26,6 +26,7 @@
 import Network.URI
 import System.Time
 import Data.List.Utils
+import Data.List(lookup)
 
 import qualified Data.ByteString.Lazy.Char8 as L
 
@@ -95,6 +96,8 @@
     copyObject aws obj (setStorageClass sc (obj {obj_headers = []}))
 
 -- | Send data for an object.
+--   If the header "Content-Length" is not set, all content must be read into
+--   memory prior to sending.
 sendObject :: AWSConnection      -- ^ AWS connection information
            -> S3Object           -- ^ Object to add to a bucket
            -> IO (AWSResult ())  -- ^ Server response
diff --git a/examples/uploadFile.hs b/examples/uploadFile.hs
--- a/examples/uploadFile.hs
+++ b/examples/uploadFile.hs
@@ -24,13 +24,16 @@
 import Data.Maybe
 import System.IO
 import qualified Data.ByteString.Lazy.Char8 as L
+import System.Posix.Files
 
 main = do argv <- getArgs
           let bucket : key : filename : xs = argv
           f <- L.readFile filename
+          contentFS <- getFileStatus filename
+          let offset = fileSize contentFS
           mConn <- amazonS3ConnectionFromEnv
           let conn = fromJust mConn
-          let obj = S3Object bucket key "text/plain" [] f
+          let obj = S3Object bucket key "text/plain" [("Content-Length",(show offset))] f
           res <- sendObject conn obj
           either (putStrLn . prettyReqError)
                  (const $ putStrLn ("Creation of " ++ key ++ " successful."))
diff --git a/hS3.cabal b/hS3.cabal
--- a/hS3.cabal
+++ b/hS3.cabal
@@ -1,5 +1,5 @@
 Name:           hS3
-Version:        0.5.5
+Version:        0.5.6
 License:        BSD3
 License-file:   LICENSE
 Cabal-Version: >= 1.6