diff --git a/csrc/sendfile_win32.c b/csrc/sendfile_win32.c
--- a/csrc/sendfile_win32.c
+++ b/csrc/sendfile_win32.c
@@ -14,4 +14,3 @@
     /* http://msdn.microsoft.com/en-us/library/ks2530z6.aspx */
     return _get_osfhandle(fd);
 }
-
diff --git a/sendfile.cabal b/sendfile.cabal
--- a/sendfile.cabal
+++ b/sendfile.cabal
@@ -1,5 +1,5 @@
 name:          sendfile
-version:       0.3
+version:       0.3.1
 stability:     experimental
 synopsis:      A portable sendfile library
 description:   A library which exposes zero-copy sendfile functionality in a portable way. If a platform does not support sendfile, a fallback implementation in haskell is provided.
diff --git a/src/Network/Socket/SendFile.hs b/src/Network/Socket/SendFile.hs
--- a/src/Network/Socket/SendFile.hs
+++ b/src/Network/Socket/SendFile.hs
@@ -16,7 +16,7 @@
          -> IO ()
 sendFile = Network.Socket.SendFile.Internal.sendFile
 
--- | A more powerful interface than sendFile, sendFile' accepts a `Handle` for the input file instead of a `FilePath` and the number of bytes you would like to read. This unlocks the full potential `Handle`(s). For instance, if you wanted to start reading from a particular offset, you could utilize `hSeek`. If you need the file size you can use 'hFileSize'.
+-- | A more powerful interface than sendFile, sendFile' accepts a `Handle` for the input file instead of a `FilePath` and the number of bytes you would like to read; this number must be a positive integer. This unlocks the full potential `Handle`(s). For instance, if you wanted to start reading from a particular offset, you could utilize `hSeek`. If you need the file size you can use 'hFileSize'.
 sendFile' :: Handle  -- ^ The output handle
           -> Handle  -- ^ The input handle
           -> Integer -- ^ The number of bytes to read
diff --git a/src/Network/Socket/SendFile/Internal.hs b/src/Network/Socket/SendFile/Internal.hs
--- a/src/Network/Socket/SendFile/Internal.hs
+++ b/src/Network/Socket/SendFile/Internal.hs
@@ -13,21 +13,21 @@
     )
 
 #if defined(WIN32_SENDFILE)
-import Network.Socket.SendFile.Win32 (sendFile')
+import Network.Socket.SendFile.Win32 (_sendFile)
 
 sendFileMode :: String
 sendFileMode = "WIN32_SENDFILE"
 #endif
 
 #if defined(LINUX_SENDFILE)
-import Network.Socket.SendFile.Linux (sendFile')
+import Network.Socket.SendFile.Linux (_sendFile)
 
 sendFileMode :: String
 sendFileMode = "LINUX_SENDFILE"
 #endif
 
 #if defined(PORTABLE_SENDFILE)
-import Network.Socket.SendFile.Portable (sendFile')
+import Network.Socket.SendFile.Portable (_sendFile)
 
 sendFileMode :: String
 sendFileMode = "PORTABLE_SENDFILE"
@@ -37,3 +37,9 @@
 sendFile outp infp = withBinaryFile infp ReadMode $ \inp -> do
     count <- hFileSize inp
     sendFile' outp inp count
+
+sendFile' :: Handle -> Handle -> Integer -> IO ()
+sendFile' outp inp count
+    | count < 0  = error "sendFile' - count must be a positive integer"
+    | count == 0 = return () -- Send nothing -- why do the work? Also, Windows treats '0' as 'send the whole file'.
+    | otherwise  = _sendFile outp inp count
diff --git a/src/Network/Socket/SendFile/Linux.hsc b/src/Network/Socket/SendFile/Linux.hsc
--- a/src/Network/Socket/SendFile/Linux.hsc
+++ b/src/Network/Socket/SendFile/Linux.hsc
@@ -1,6 +1,6 @@
 {-# LANGUAGE ForeignFunctionInterface #-}
 -- | Linux system-dependent code for 'sendfile'.
-module Network.Socket.SendFile.Linux (sendFile') where
+module Network.Socket.SendFile.Linux (_sendFile) where
 import Data.Int
 import Data.Word
 import Foreign.C.Error (throwErrno)
@@ -10,8 +10,8 @@
 
 #include <sys/sendfile.h>
 
-sendFile' :: Handle -> Handle -> Integer -> IO ()
-sendFile' outp inp count = do
+_sendFile :: Handle -> Handle -> Integer -> IO ()
+_sendFile outp inp count = do
     -- flush outp before sending
     hFlush outp
     withHandle_ "Network.Socket.SendFile.Linux.sendFile'" outp $ \outp' -> do
@@ -23,5 +23,5 @@
         then throwErrno "Network.Socket.SendFile.Linux.sendFile'"
         else return ()
 
-foreign import ccall
+foreign import ccall unsafe
     c_sendfile_linux :: FD -> FD -> (#type size_t) -> IO (#type ssize_t)
diff --git a/src/Network/Socket/SendFile/Portable.hs b/src/Network/Socket/SendFile/Portable.hs
--- a/src/Network/Socket/SendFile/Portable.hs
+++ b/src/Network/Socket/SendFile/Portable.hs
@@ -1,5 +1,5 @@
 -- | Portable implementation of sendfile.
-module Network.Socket.SendFile.Portable (sendFile') where
+module Network.Socket.SendFile.Portable (_sendFile) where
 
 import Data.ByteString.Char8
 import Prelude hiding (readFile)
@@ -7,7 +7,7 @@
 
 
 -- FIXME: possibly immature / inefficient implementation
-sendFile' :: Handle -> Handle -> Integer -> IO ()
-sendFile' outp inp count = do
+_sendFile :: Handle -> Handle -> Integer -> IO ()
+_sendFile outp inp count = do
     hPutStr outp =<< hGet inp (fromIntegral count)
     hFlush outp -- match the behavior that all data is "flushed to the os" of native implementations
diff --git a/src/Network/Socket/SendFile/Win32.hsc b/src/Network/Socket/SendFile/Win32.hsc
--- a/src/Network/Socket/SendFile/Win32.hsc
+++ b/src/Network/Socket/SendFile/Win32.hsc
@@ -1,6 +1,6 @@
 {-# LANGUAGE ForeignFunctionInterface #-}
 -- | Win32 system-dependent code for 'TransmitFile'.
-module Network.Socket.SendFile.Win32 (sendFile') where
+module Network.Socket.SendFile.Win32 (_sendFile) where
 import Data.Int
 import Data.Word
 import Foreign.C.Error (throwErrno)
@@ -12,8 +12,8 @@
 
 #include <windows.h>
 
-sendFile' :: Handle -> Handle -> Integer -> IO ()
-sendFile' outp inp count = do
+_sendFile :: Handle -> Handle -> Integer -> IO ()
+_sendFile outp inp count = do
     hFlush outp -- flush the buffer before invoking transmitFile
     withHandle_ "Network.Socket.SendFile.Win32.sendFile'" outp $ \outp' -> do
     withHandle_ "Network.Socket.SendFile.Win32.sendFile'" inp $ \inp' -> do
@@ -36,8 +36,8 @@
 transmitFile out_fd in_hdl count =
     failIf_ (== 0) "Network.Socket.SendFile.Win32.transmitFile" (c_TransmitFile out_fd in_hdl count)
     
-foreign import ccall
+foreign import ccall unsafe
     c_get_osfhandle :: FD -> IO IntPtr
     
-foreign import ccall
+foreign import ccall unsafe
     c_TransmitFile :: FD -> HANDLE -> DWORD -> IO (#type BOOL)