diff --git a/Network/Wai/Logger/Date.hs b/Network/Wai/Logger/Date.hs
--- a/Network/Wai/Logger/Date.hs
+++ b/Network/Wai/Logger/Date.hs
@@ -45,7 +45,7 @@
         return $ zonedDate cache
     else do
         newCache <- newDate newEt
-        !_ <- atomicModifyIORef ref (\_ -> (newCache, ()))
+        writeIORef ref newCache
         return $ zonedDate newCache
 
 newDate :: TIME -> IO DateCache
diff --git a/wai-logger.cabal b/wai-logger.cabal
--- a/wai-logger.cabal
+++ b/wai-logger.cabal
@@ -1,5 +1,5 @@
 Name:                   wai-logger
-Version:                0.1.1
+Version:                0.1.2
 Author:                 Kazu Yamamoto <kazu@iij.ad.jp>
 Maintainer:             Kazu Yamamoto <kazu@iij.ad.jp>
 License:                BSD3