diff --git a/objective.cabal b/objective.cabal
--- a/objective.cabal
+++ b/objective.cabal
@@ -2,7 +2,7 @@
 -- documentation, see http://haskell.org/cabal/users-guide/
 
 name:                objective
-version:             0.0.1
+version:             0.0.2
 synopsis:            Extensible objects
 description:         Stateful effect transducer
 homepage:            https://github.com/fumieval/objective
diff --git a/src/Control/Object.hs b/src/Control/Object.hs
--- a/src/Control/Object.hs
+++ b/src/Control/Object.hs
@@ -7,6 +7,7 @@
 import Control.Monad.Trans.State
 import Control.Monad
 import Data.Typeable
+import Control.Applicative
 
 -- | The type 'Object e m' represents objects which can handle messages 'e', perform actions in the environment 'm'.
 -- It can be thought of as a function between effects.
@@ -22,7 +23,7 @@
 transObject f (Object m) = Object $ fmap (fmap (transObject f)) . f . m
 
 -- | Apply a function to the messages coming into the object.
-adaptObject :: Functor f => (forall x. e x -> f x) -> Object f m -> Object e m
+adaptObject :: Functor m => (forall x. e x -> f x) -> Object f m -> Object e m
 adaptObject f (Object m) = Object $ fmap (fmap (adaptObject f)) . m . f
 
 -- | Parrots messages given.