diff --git a/Changelog.md b/Changelog.md
--- a/Changelog.md
+++ b/Changelog.md
@@ -1,33 +1,37 @@
+### 0.4.1.0
+
+- Bugfix: keep calling *fdWriteBuf* until it writes complete buffer.
+
 ### 0.4.0.0
 
-- all asynchronous handlers can now report events via eventfd channels
-- new dependency on package *binary* (>= 0.8.1.0)
+- All asynchronous handlers can now report events via eventfd channels.
+- New dependency on package *binary* (>= 0.8.1.0).
 
 ### 0.3.2.2
 
-- stricter constraints for packages *base* (>= 4.8 && < 5) and
-  *template-haskell* (>= 2.11.0.0)
+- Stricter constraints for packages *base* (>= 4.8 && < 5) and
+  *template-haskell* (>= 2.11.0.0).
 
 ### 0.3.2.0
 
-- versioning security: get number of required version parts from C code.
+- Versioning security: get number of required version parts from C code.
 
 ### 0.3.1.0
 
-- added versioning support to test for compatibility in C code.
+- Added versioning support to test for compatibility in C code.
 
 ### 0.3.0.0
 
-- added an asynchronous client request body handler exported with
+- Added an asynchronous client request body handler exported with
   *ngxExportAsyncOnReqBody* for using in a new Nginx directive
   *haskell_run_async_on_request_body*.
 
 ### 0.2.5.1
 
-- added signatures for type-checkers and exporters to prevent warnings when
+- Added signatures for type-checkers and exporters to prevent warnings when
   reifying in a user code with *-Wmissing-signatures* or *-Wall* enabled.
 
 ### 0.2.5.0
 
-- added a synchronous handler in IO Monad exported with *ngxExportIOYY*.
+- Added a synchronous handler in IO Monad exported with *ngxExportIOYY*.
 
diff --git a/NgxExport.hs b/NgxExport.hs
--- a/NgxExport.hs
+++ b/NgxExport.hs
@@ -48,6 +48,7 @@
 import           System.Posix.IO
 import           Control.Monad
 import           Control.Exception hiding (Handler)
+import           GHC.IO.Exception (ioe_errno)
 import           Control.Concurrent.Async
 import           Data.Maybe
 import qualified Data.ByteString as B
@@ -58,10 +59,11 @@
 import           Paths_ngx_export (version)
 import           Data.Version
 
-pattern I l <- (fromIntegral -> l)
-pattern PtrLen s l <- (s, I l)
+pattern I i                 <- (fromIntegral -> i)
+pattern PtrLen s l          <- (s, I l)
 pattern PtrLenFromMaybe s l <- (fromMaybe (nullPtr, -1) -> PtrLen s l)
-pattern EmptyLBS <- (L.null -> True)
+pattern ToBool i            <- ((/= 0) -> i)
+pattern EmptyLBS            <- (L.null -> True)
 
 data NgxExport = SS            (String -> String)
                | SSS           (String -> String -> String)
@@ -384,22 +386,33 @@
                 )
     )
     `finally`
-    ((if efd
-          then void $ B.unsafeUseAsCString asyncIOFlag8b
-                         (\(castPtr -> s) -> fdWriteBuf fd s 8)
-          else B.unsafeUseAsCString asyncIOFlag1b
-                         (\(castPtr -> s) -> fdWriteBuf fd s 1) >> closeFd fd
-     ) `catchIOError` const (return ())
+    (let writeBufN n s w
+             | w < n = (w +) <$>
+                 fdWriteBuf fd (plusPtr s $ fromIntegral w) (n - w)
+                 `catchIOError`
+                 (\e -> return $
+                      if ioe_errno e == Just ((\(Errno e) -> e) eINTR)
+                          then 0
+                          else n
+                 ) >>= writeBufN n s
+             | otherwise = return w
+         writeFlag1b = void $
+             B.unsafeUseAsCString asyncIOFlag1b $ flip (writeBufN 1) 0
+         writeFlag8b = void $
+             B.unsafeUseAsCString asyncIOFlag8b $ flip (writeBufN 8) 0
+     in if efd
+            then writeFlag8b
+            else writeFlag1b >> closeFd fd `catchIOError` const (return ())
     )
 
 asyncIOYY :: NgxExport -> CString -> CInt ->
     CInt -> CUInt -> CUInt -> Ptr CString -> Ptr CSize -> Ptr CUInt -> IO ()
-asyncIOYY (IOYY f) x (I n) fd ((/= 0) -> efd) ((/= 0) -> fstRun) =
+asyncIOYY (IOYY f) x (I n) fd (ToBool efd) (ToBool fstRun) =
     asyncIOCommon (B.unsafePackCStringLen (x, n) >>= flip f fstRun) fd efd
 
 asyncIOYYY :: NgxExport -> Ptr NgxStrType -> CInt -> CString -> CInt ->
     CInt -> CUInt -> Ptr CString -> Ptr CSize -> Ptr CUInt -> IO ()
-asyncIOYYY (IOYYY f) b (I m) x (I n) fd ((/= 0) -> efd) =
+asyncIOYYY (IOYYY f) b (I m) x (I n) fd (ToBool efd) =
     asyncIOCommon
     (do
         b' <- peekNgxStringArrayLenY b m
diff --git a/ngx-export.cabal b/ngx-export.cabal
--- a/ngx-export.cabal
+++ b/ngx-export.cabal
@@ -1,5 +1,5 @@
 name:                ngx-export
-version:             0.4.0.0
+version:             0.4.1.0
 synopsis:            Helper module for Nginx haskell module
 description:         Helper module for
         <http://github.com/lyokha/nginx-haskell-module Nginx haskell module>