diff --git a/Network/Sendfile/Linux.hsc b/Network/Sendfile/Linux.hsc
--- a/Network/Sendfile/Linux.hsc
+++ b/Network/Sendfile/Linux.hsc
@@ -18,7 +18,7 @@
 import Foreign.Marshal (alloca)
 import Foreign.Ptr (Ptr, plusPtr, castPtr)
 import Foreign.ForeignPtr
-import Foreign.Storable (poke)
+import Foreign.Storable (poke, sizeOf)
 import GHC.Conc (threadWaitWrite)
 import Network.Sendfile.Types
 import Network.Socket
@@ -29,6 +29,11 @@
 #include <sys/sendfile.h>
 #include <sys/socket.h>
 
+safeSize :: CSize
+safeSize
+  | sizeOf (0 :: CSize) == 8 = 2^(60 :: Int)
+  | otherwise                = 2^(30 :: Int)
+
 ----------------------------------------------------------------
 
 -- |
@@ -90,7 +95,10 @@
 sendfileloop dst src offp len hook = do
     -- Multicore IO manager use edge-trigger mode.
     -- So, calling threadWaitWrite only when errnor is eAGAIN.
-    bytes <- c_sendfile dst src offp len
+    let toSend
+          | len > safeSize = safeSize
+          | otherwise      = len
+    bytes <- c_sendfile dst src offp toSend
     case bytes of
         -1 -> do
             errno <- getErrno
diff --git a/simple-sendfile.cabal b/simple-sendfile.cabal
--- a/simple-sendfile.cabal
+++ b/simple-sendfile.cabal
@@ -1,5 +1,5 @@
 Name:                   simple-sendfile
-Version:                0.2.18
+Version:                0.2.19
 Author:                 Kazu Yamamoto <kazu@iij.ad.jp>
 Maintainer:             Kazu Yamamoto <kazu@iij.ad.jp>
 License:                BSD3