diff --git a/Data/UnixTime.hs b/Data/UnixTime.hs
--- a/Data/UnixTime.hs
+++ b/Data/UnixTime.hs
@@ -13,7 +13,7 @@
   , webDateFormat
   , mailDateFormat
   -- * Difference time
-  , UnixDiffTime
+  , UnixDiffTime(..)
   , diffUnixTime
   , addUnixDiffTime
   , secondsToUnixDiffTime
diff --git a/Data/UnixTime/Types.hs b/Data/UnixTime/Types.hs
--- a/Data/UnixTime/Types.hs
+++ b/Data/UnixTime/Types.hs
@@ -8,9 +8,9 @@
 -- |
 -- Data structure for Unix time.
 data UnixTime = UnixTime {
-  -- | Seconds from 1st Jan 1970
+    -- | Seconds from 1st Jan 1970
     utSeconds :: {-# UNPACK #-} !CTime
-  -- | Micro seconds (i.e. 10^(-6))
+    -- | Micro seconds (i.e. 10^(-6))
   , utMicroSeconds :: {-# UNPACK #-} !Int32
   } deriving (Eq,Ord,Show)
 
@@ -28,5 +28,9 @@
 -- >>> (3 :: UnixDiffTime) * 2
 -- UnixDiffTime 6 0
 
-data UnixDiffTime = UnixDiffTime {-# UNPACK #-} !CTime
-                                 {-# UNPACK #-} !Int32 deriving (Eq,Ord,Show)
+data UnixDiffTime = UnixDiffTime {
+    -- | Seconds from 1st Jan 1970
+    udtSeconds :: {-# UNPACK #-} !CTime
+    -- | Micro seconds (i.e. 10^(-6))
+  , udtMicroSecnods :: {-# UNPACK #-} !Int32
+  } deriving (Eq,Ord,Show)
diff --git a/unix-time.cabal b/unix-time.cabal
--- a/unix-time.cabal
+++ b/unix-time.cabal
@@ -1,5 +1,5 @@
 Name:                   unix-time
-Version:                0.1.6
+Version:                0.1.7
 Author:                 Kazu Yamamoto <kazu@iij.ad.jp>
 Maintainer:             Kazu Yamamoto <kazu@iij.ad.jp>
 License:                BSD3