diff --git a/ChangeLog.md b/ChangeLog.md
--- a/ChangeLog.md
+++ b/ChangeLog.md
@@ -1,3 +1,7 @@
+## 1.4.4
+
+* Fixing a bug of reverse index.
+
 ## 1.4.3
 
 * Priority benchmark is now external information versions.
diff --git a/Network/HPACK/Table/RevIndex.hs b/Network/HPACK/Table/RevIndex.hs
--- a/Network/HPACK/Table/RevIndex.hs
+++ b/Network/HPACK/Table/RevIndex.hs
@@ -1,7 +1,9 @@
+{-# LANGUAGE BangPatterns #-}
+
 module Network.HPACK.Table.RevIndex where
 
-import Data.Map (Map)
-import qualified Data.Map as M
+import Data.Map.Strict (Map)
+import qualified Data.Map.Strict as M
 import Network.HPACK.Types
 import Network.HPACK.Table.Static
 
@@ -14,27 +16,31 @@
 newtype Outer = Outer (Map HeaderName Inner) deriving Show
 
 defaultRevIndex :: Outer
-defaultRevIndex = Outer $ foldr op M.empty lst
+defaultRevIndex = Outer $! foldr op M.empty lst
   where
     lst = zip staticTableList $ map SIndex [1..]
     op ((k,v),i) m = M.alter f k m
       where
-        f Nothing              = Just $ Inner [(v,i)]    []
-        f (Just (Inner ss ds)) = Just $ Inner ((v,i):ss) ds
+        f Nothing              = Just $! Inner [(v,i)]    []
+        f (Just (Inner ss ds)) = let ss' = (v,i):ss
+                                 in Just $! Inner ss' ds
 
 insertDynamic :: Header -> DIndex -> Outer -> Outer
-insertDynamic (k,v) didx (Outer rev) = Outer $ M.alter f k rev
+insertDynamic (k,v) didx (Outer rev) = Outer $! M.alter f k rev
   where
-    f Nothing              = Just $ Inner [] [(v,didx)]
-    f (Just (Inner ss ds)) = Just $ Inner ss ((v,didx):ds)
+    f Nothing              = Just $! Inner [] [(v,didx)]
+    f (Just (Inner ss ds)) = let ds' = (v,didx):ds
+                             in Just $! Inner ss ds'
 
 deleteDynamic :: Header -> Map HeaderName Inner -> Map HeaderName Inner
 deleteDynamic (k,v) rev = M.alter f k rev
   where
     f Nothing              = Nothing
     f (Just (Inner ss ds)) = case filter (\(a,_) -> a /= v) ds of
-        []  -> Nothing
-        ds' -> Just $ Inner ss ds'
+        []  -> case ss of
+            [] -> Nothing
+            _  -> Just $! Inner ss []
+        ds' -> Just $! Inner ss ds'
 
 deleteDynamicList :: [Header] -> Outer -> Outer
-deleteDynamicList hs (Outer rev) = Outer $ foldr deleteDynamic rev hs
+deleteDynamicList hs (Outer rev) = Outer $! foldr deleteDynamic rev hs
diff --git a/bench-hpack/Main.hs b/bench-hpack/Main.hs
new file mode 100644
--- /dev/null
+++ b/bench-hpack/Main.hs
@@ -0,0 +1,53 @@
+{-# LANGUAGE BangPatterns #-}
+
+module Main where
+
+import Control.Exception
+import Criterion.Main
+import Network.HPACK
+import Data.ByteString (ByteString)
+
+main :: IO ()
+main = do
+    hdrs <- read <$> readFile "bench-hpack/headers.hs"
+    hpacks <- prepare hdrs
+    _ <- evaluate hpacks
+    defaultMain [
+        bgroup "HPACK encoding" [
+              bench "Pure" $ nfIO (enc hdrs)
+            ]
+      , bgroup "HPACK decoding" [
+              bench "Pure" $ nfIO (dec hpacks)
+            ]
+      ]
+
+----------------------------------------------------------------
+prepare :: [HeaderList] -> IO [ByteString]
+prepare hdrs = do
+    tbl <- newDynamicTableForEncoding defaultDynamicTableSize
+    go tbl hdrs id
+  where
+    go _    []     b = return (b [])
+    go !tbl (h:hs) b = do
+        (tbl', frag) <- encodeHeader defaultEncodeStrategy tbl h
+        go tbl' hs (b . (frag :))
+
+enc :: [HeaderList] -> IO ()
+enc hdrs = do
+    tbl <- newDynamicTableForEncoding defaultDynamicTableSize
+    go tbl hdrs
+  where
+    go _    []     = return ()
+    go !tbl (h:hs) = do
+        (tbl', !_) <- encodeHeader defaultEncodeStrategy tbl h
+        go tbl' hs
+
+dec :: [ByteString] -> IO ()
+dec hpacks = do
+    tbl <- newDynamicTableForDecoding defaultDynamicTableSize
+    go tbl hpacks
+  where
+    go _    []     = return ()
+    go !tbl (f:fs) = do
+        (tbl', !_) <- decodeHeader tbl f
+        go tbl' fs
diff --git a/http2.cabal b/http2.cabal
--- a/http2.cabal
+++ b/http2.cabal
@@ -1,5 +1,5 @@
 Name:                   http2
-Version:                1.4.3
+Version:                1.4.4
 Author:                 Kazu Yamamoto <kazu@iij.ad.jp>
 Maintainer:             Kazu Yamamoto <kazu@iij.ad.jp>
 License:                BSD3
@@ -120,7 +120,6 @@
                       , containers
                       , hex
                       , hspec >= 1.3
-                      , mwc-random
                       , psqueues
                       , stm
                       , unordered-containers
@@ -261,7 +260,7 @@
                       , text
                       , unordered-containers
 
-Benchmark criterion
+Benchmark priority
   Type:                 exitcode-stdio-1.0
   Default-Language:     Haskell2010
   Hs-Source-Dirs:       bench-priority, .
@@ -274,7 +273,6 @@
                         RandomSkewHeap
                         RingOfQueues
                         RingOfQueuesSTM
-
   Build-Depends:        base
                       , array
                       , containers
@@ -284,4 +282,18 @@
                       , mwc-random
                       , psqueues
                       , random
+                      , stm
+
+Benchmark header-compression
+  Type:                 exitcode-stdio-1.0
+  Default-Language:     Haskell2010
+  Hs-Source-Dirs:       bench-hpack, .
+  Ghc-Options:          -Wall
+  Main-Is:              Main.hs
+  Build-Depends:        base
+                      , array
+                      , bytestring
+                      , containers
+                      , criterion
+                      , hashtables
                       , stm