diff --git a/Control/MonadPlus/Indexed/Free.hs b/Control/MonadPlus/Indexed/Free.hs
--- a/Control/MonadPlus/Indexed/Free.hs
+++ b/Control/MonadPlus/Indexed/Free.hs
@@ -1,4 +1,4 @@
-{-# LANGUAGE GADTs, FlexibleInstances #-}
+{-# LANGUAGE GADTs, FlexibleInstances, MultiParamTypeClasses #-}
 module Control.MonadPlus.Indexed.Free (IxFree(..), module Control.Monad.Indexed.Free.Class) where
 
 import Control.Applicative
@@ -36,6 +36,9 @@
   l `implus` Plus [] = l
   Plus as `implus` Plus bs = Plus (as ++ bs)
   a `implus` b = Plus [a, b]
+
+instance IxFunctor f => IxMonadFree f (IxFree f) where
+    iwrap = Free
 
 instance IxFunctor f => Functor (IxFree f i i) where
     fmap = imap
diff --git a/indexed-free.cabal b/indexed-free.cabal
--- a/indexed-free.cabal
+++ b/indexed-free.cabal
@@ -1,5 +1,5 @@
 name:                indexed-free
-version:             0.3.0
+version:             0.3.1
 synopsis:            indexed monads for free
 description:         A free indexed monad
 homepage:            https://github.com/fumieval/indexed-free