diff --git a/CHANGELOG.md b/CHANGELOG.md
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -1,5 +1,9 @@
 # Revision history for monadic-recursion-schemes
 
+## 0.1.9.1 -- 2020-05-17
+
+* no warning at build time.
+
 ## 0.1.9.0 -- 2020-05-16
 
 * add iterateM (as dual of cascadeM)
diff --git a/monadic-recursion-schemes.cabal b/monadic-recursion-schemes.cabal
--- a/monadic-recursion-schemes.cabal
+++ b/monadic-recursion-schemes.cabal
@@ -4,7 +4,7 @@
 -- http://haskell.org/cabal/users-guide/
 
 name:                monadic-recursion-schemes
-version:             0.1.9.0
+version:             0.1.9.1
 synopsis:            Recursion Schemes for Monadic version.
 description:         Yet another recursion schemes for monadic style, depends on recursion-schemes.
 homepage:            https://github.com/cutsea110/monadic-recursion-schemes.git
@@ -37,6 +37,7 @@
                        free >=5.1.3
   hs-source-dirs:      src
   default-language:    Haskell2010
+  ghc-options:         -Wall
 
 test-suite monadic-recursion-schemes-test
   default-language:    Haskell2010
diff --git a/src/Data/Functor/Foldable/Monadic.hs b/src/Data/Functor/Foldable/Monadic.hs
--- a/src/Data/Functor/Foldable/Monadic.hs
+++ b/src/Data/Functor/Foldable/Monadic.hs
@@ -1,40 +1,47 @@
-{-# LANGUAGE GADTs #-}
-{-# LANGUAGE LambdaCase #-}
-{-# LANGUAGE DeriveFunctor #-}
+{-# LANGUAGE AllowAmbiguousTypes #-}
 {-# LANGUAGE DeriveFoldable #-}
+{-# LANGUAGE DeriveFunctor #-}
 {-# LANGUAGE DeriveTraversable #-}
 {-# LANGUAGE FlexibleContexts #-}
-{-# LANGUAGE AllowAmbiguousTypes #-}
+{-# LANGUAGE GADTs #-}
+{-# LANGUAGE LambdaCase #-}
 {-# LANGUAGE ScopedTypeVariables #-}
 module Data.Functor.Foldable.Monadic
-  ( cataM, anaM
-  , paraM, apoM
-  , histoM, futuM
-  , histoM', futuM'
-  , zygoM, cozygoM
+  ( -- * Folding
+    cataM
+  , preproM
+  , paraM
+  , zygoM
+  , histoM, histoM'
+  , dynaM, dynaM', dynaM''
+
+    -- * Unfolding
+  , anaM
+  , postproM
+  , apoM
+  , cozygoM
+  , futuM, futuM'
+  , codynaM, codynaM', codynaM''
+
+    -- * Refolding
   , hyloM, metaM
   , hyloM', metaM'
   , chronoM, cochronoM
   , chronoM' -- cochronoM'
-  , dynaM, codynaM
-  , dynaM', codynaM'
-  , dynaM'', codynaM''
+
+    -- * Others
   , mutuM, comutuM
   , mutuM', comutuM'
-  , preproM, postproM
   , cascadeM, iterateM
   ) where
 
 import           Control.Comonad              (Comonad (..))
 import           Control.Comonad.Cofree       (Cofree (..))
-import qualified Control.Comonad.Trans.Cofree as Cf (CofreeF (..))
+import qualified Control.Comonad.Trans.Cofree as CF (CofreeF (..))
 import           Control.Monad                ((<=<), liftM2)
 import           Control.Monad.Free           (Free (..))
-import qualified Control.Monad.Trans.Free     as Fr (FreeF (..))
-import           Control.Monad.Trans.Class    (lift)
-import           Control.Monad.Trans.Reader   (ReaderT, ask, runReaderT)
-import           Data.Functor.Foldable        (Recursive (..), Corecursive (..), Base, Fix (..))
-
+import qualified Control.Monad.Trans.Free     as FR (FreeF (..))
+import           Data.Functor.Foldable        (Recursive (..), Corecursive (..), Base)
 
 -- | catamorphism
 cataM :: (Monad m, Traversable (Base t), Recursive t)
@@ -70,7 +77,7 @@
        -> t -> m a
 histoM phi = h
   where h = phi <=< mapM f . project
-        f = anaM (liftM2 (Cf.:<) <$> h <*> return . project)
+        f = anaM (liftM2 (CF.:<) <$> h <*> return . project)
 
 -- | histomorphism on catamorphism variant
 histoM' :: (Monad m, Traversable (Base t), Recursive t)
@@ -86,8 +93,8 @@
 futuM psi = h
   where h = return . embed <=< mapM f <=< psi
         f = cataM $ \case
-          Fr.Pure  a -> h a
-          Fr.Free fb -> return (embed fb)
+          FR.Pure  a -> h a
+          FR.Free fb -> return (embed fb)
 
 -- | futumorphism on anamorphism variant
 futuM' :: (Monad m, Traversable (Base t), Corecursive t)
@@ -133,7 +140,7 @@
       => (Base t t -> m t)   -- ^ algebra
       -> (s -> m (Base s s)) -- ^ coalgebra
       -> s -> m t
-metaM phi psi = h
+metaM _phi _psi = h
   where h = return . embed <=< mapM h . project
 
 -- | metamorphism on combination variant of cata to ana
@@ -217,7 +224,7 @@
       => (Base t (a, b) -> m b) -- ^ algebra
       -> (Base t (a, b) -> m a) -- ^ algebra
       -> t -> m b
-mutuM g f = v g f
+mutuM q p = v q p
   where u f g = f <=< mapM (liftM2 (,) <$> u f g <*> v g f) . project
         v g f = g <=< mapM (liftM2 (,) <$> u f g <*> v g f) . project
 
@@ -233,7 +240,7 @@
         => (b -> m (Base t (Either a b))) -- ^ coalgebra
         -> (a -> m (Base t (Either a b))) -- ^ coalgebra
         -> b -> m t
-comutuM g f = v g f
+comutuM q p = v q p
   where u f g = fmap embed . mapM (either (u f g) (v g f)) <=< f
         v g f = fmap embed . mapM (either (u f g) (v g f)) <=< g