diff --git a/miku.cabal b/miku.cabal
--- a/miku.cabal
+++ b/miku.cabal
@@ -1,5 +1,5 @@
 Name:                 miku
-Version:              2011.6.15
+Version:              2011.6.18
 Build-type:           Simple
 Synopsis:             A minimum web dev DSL in Haskell
 Description:
@@ -22,7 +22,7 @@
                     , hack2 >= 2011.6.10
                     , hack2-contrib >= 2011.6.11
                     , utf8-string
-                    , air >= 2011.6.11
+                    , air >= 2011.6.18
                     , mtl
                     , containers
                     , bytestring
diff --git a/src/Network/Miku/Type.hs b/src/Network/Miku/Type.hs
--- a/src/Network/Miku/Type.hs
+++ b/src/Network/Miku/Type.hs
@@ -24,15 +24,7 @@
   , mimes           :: [(ByteString, ByteString)]
   }
 
-
-instance Default MikuState where
-  def = MikuState 
-    {
-      middlewares = def
-    , router = def
-    , mimes = def
-    }
-
+mkDefault ''MikuState
 mkLabel ''MikuState
 
 type MikuMonadT a = State MikuState a