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:                0.4.3
+Version:                0.4.4
 Author:                 Kazu Yamamoto <kazu@iij.ad.jp>
 Maintainer:             Kazu Yamamoto <kazu@iij.ad.jp>
 License:                BSD3
@@ -36,6 +36,7 @@
                       , bytestring
                       , old-time
                       , binary
+  Build-Tools:          hsc2hs
   C-Sources:            cbits/conv.c
   if os(windows)
     C-Sources:          cbits/strftime.c