diff --git a/package.yaml b/package.yaml
index 59f0218..9040996 100644
--- a/package.yaml
+++ b/package.yaml
@@ -42,3 +42,4 @@ tests:
     - tasty-hunit
     - tasty-quickcheck
     - tasty-th
+    - deepseq
diff --git a/src/Data/ByteString/Lazy/Encoding/Internal.hs b/src/Data/ByteString/Lazy/Encoding/Internal.hs
index 482e671..4d89674 100644
--- a/src/Data/ByteString/Lazy/Encoding/Internal.hs
+++ b/src/Data/ByteString/Lazy/Encoding/Internal.hs
@@ -127,7 +127,7 @@ decodeWith Enc.TextEncoding{ .. } inBufSize outBufSize b = TL.fromChunks $ unsaf
                       moveBytes (q `plusPtr` bufR buf) p (bufferAvailable buf)
                       go (B.drop (bufferAvailable buf) b : bs) buf{ bufR = bufR buf + bufferAvailable buf }
 
-      flushOutBuf :: CharBuffer -> Ptr Word16 -> IO ([T.Text], CharBuffer)
+      flushOutBuf :: CharBuffer -> ForeignPtr Word16 -> IO ([T.Text], CharBuffer)
       flushOutBuf buf workspace
         | isEmptyBuffer buf = return ([], buf{ bufL=0, bufR=0 })
         | charSize==2 = do
@@ -136,7 +136,8 @@ decodeWith Enc.TextEncoding{ .. } inBufSize outBufSize b = TL.fromChunks $ unsaf
                   p' = castPtr p
               t <- T.fromPtr (p' `plusPtr` bufL buf) (fromIntegral (bufferElems buf))
               return ([t], buf{ bufL=0, bufR=0 })
-        | otherwise = do
+        | otherwise =
+            withForeignPtr workspace $ \workspace' ->
             withBuffer buf $ \p -> do
               let p' :: Ptr Char
                   p' = castPtr p
@@ -145,18 +146,18 @@ decodeWith Enc.TextEncoding{ .. } inBufSize outBufSize b = TL.fromChunks $ unsaf
                     | otherwise = do
                         c <- liftM fromEnum $ peekElemOff p' i
                         if c < 0x10000 then do
-                          pokeElemOff workspace j (fromIntegral c)
+                          pokeElemOff workspace' j (fromIntegral c)
                           f (i+1) (j+1)
                         else do
                           let c' = c - 0x10000
-                          pokeElemOff workspace j (fromIntegral (c' `div` 0x400 + 0xd800))
-                          pokeElemOff workspace (j+1) (fromIntegral (c' `mod` 0x400 + 0xdc00))
+                          pokeElemOff workspace' j (fromIntegral (c' `div` 0x400 + 0xd800))
+                          pokeElemOff workspace' (j+1) (fromIntegral (c' `mod` 0x400 + 0xdc00))
                           f (i+1) (j+2)
               n <- f (bufL buf) 0
-              t <- T.fromPtr workspace (fromIntegral n)
+              t <- T.fromPtr workspace' (fromIntegral n)
               return ([t], buf{ bufL=0, bufR=0 })
 
-      loop :: [B.ByteString] -> Buffer Word8 -> CharBuffer -> Ptr Word16 -> IO [T.Text]
+      loop :: [B.ByteString] -> Buffer Word8 -> CharBuffer -> ForeignPtr Word16 -> IO [T.Text]
       loop bs inBuf outBuf workspace = do
         (bs', inBuf1) <- fillInBuf bs inBuf
         if isEmptyBuffer inBuf1 then do
@@ -190,8 +191,5 @@ decodeWith Enc.TextEncoding{ .. } inBufSize outBufSize b = TL.fromChunks $ unsaf
 
   inBuf <- newByteBuffer inBufSize ReadBuffer
   outBuf <- newCharBuffer outBufSize WriteBuffer
-  if charSize == 2 then do
-    loop (BL.toChunks b) inBuf outBuf nullPtr
-  else do
-    allocaArray (outBufSize * 2) $ \workspace ->
-      loop (BL.toChunks b) inBuf outBuf workspace
+  workspace <- if charSize == 2 then newForeignPtr_ nullPtr else mallocForeignPtrArray (outBufSize * 2)
+  loop (BL.toChunks b) inBuf outBuf workspace
diff --git a/test/Base.hs b/test/Base.hs
index 91e5222..bd71b75 100644
--- a/test/Base.hs
+++ b/test/Base.hs
@@ -4,14 +4,17 @@
 {-# LANGUAGE TemplateHaskell #-}
 module Base (baseTestGroup) where
 
+import Control.DeepSeq
 import qualified Data.ByteString.Lazy.Encoding as Enc
 import qualified Data.ByteString.Lazy.Encoding.Internal as Enc
 import qualified Data.ByteString.Lazy as BL
+import qualified Data.ByteString as B
 import qualified Data.Text.Lazy as TL
 import qualified Data.Text.Lazy.Encoding as TL
 
 import Test.Tasty
 import Test.Tasty.QuickCheck
+import Test.Tasty.HUnit
 import Test.Tasty.TH
 
 checkEncode :: Enc.TextEncoding -> (TL.Text -> BL.ByteString) -> Property
@@ -62,6 +65,13 @@ prop_encode_decode_utf32le = checkRoundTrip Enc.utf32le
 prop_encode_decode_utf32be :: Property
 prop_encode_decode_utf32be = checkRoundTrip Enc.utf32be
 
+case_decoding_long_chunked_string :: IO ()
+case_decoding_long_chunked_string = do
+  let ls = [32752, 32752, 32752, 32752, 32752, 32752, 32752, 32752, 32752, 18193]
+      bs = BL.fromChunks [B.pack (replicate l (fromIntegral (fromEnum 'a'))) | l <- ls]
+  let t = Enc.decode Enc.utf8 bs
+  deepseq t $ return ()
+
 -- ---------------------------------------------------------------------
 
 baseTestGroup :: TestTree