diff --git a/System/Log/FastLogger/LogStr.hs b/System/Log/FastLogger/LogStr.hs
--- a/System/Log/FastLogger/LogStr.hs
+++ b/System/Log/FastLogger/LogStr.hs
@@ -29,7 +29,7 @@
 #endif
 import Data.String (IsString(..))
 import Data.Int (Int8,Int16,Int32,Int64)
-import Data.Word (Word8,Word16,Word32,Word64)
+import Data.Word (Word,Word8,Word16,Word32,Word64)
 import qualified Data.Text as T
 import qualified Data.Text.Encoding as T
 import qualified Data.Text.Lazy as TL
diff --git a/fast-logger.cabal b/fast-logger.cabal
--- a/fast-logger.cabal
+++ b/fast-logger.cabal
@@ -1,5 +1,5 @@
 Name:                   fast-logger
-Version:                2.4.14
+Version:                2.4.15
 Author:                 Kazu Yamamoto <kazu@iij.ad.jp>
 Maintainer:             Kazu Yamamoto <kazu@iij.ad.jp>
 License:                BSD3
@@ -44,6 +44,7 @@
 
     Ghc-Options:     -Wall -threaded
     Other-Modules:   FastLoggerSpec
+    Build-Tools:     hspec-discover >= 2.6
     Build-Depends:   base >= 4 && < 5
                    , bytestring
                    , directory