diff --git a/src/Plugin/TypeCheck/Nat/Simple.hs b/src/Plugin/TypeCheck/Nat/Simple.hs
--- a/src/Plugin/TypeCheck/Nat/Simple.hs
+++ b/src/Plugin/TypeCheck/Nat/Simple.hs
@@ -27,8 +27,9 @@
 --   >		=<< (,) <$> (givens =<< decodeAll gs) <*> (wanted =<< decode w)
 
 plugin :: Plugin
-plugin = typeCheckWith @L "Plugin.TypeCheck.Nat.Simple" \occ gs _ w -> do
+plugin = typeCheckWith @L "Plugin.TypeCheck.Nat.Simple" \occ gs d w -> do
 	tell @L $ "givens: " .+. fromSDoc (ppr gs)
+	tell @L $ "derived: " .+. fromSDoc (ppr d)
 	tell @L $ "wanted: " .+. fromSDoc (ppr w)
 	uncurry canDerive
 		=<< (,) <$> (givens =<< decodeAll occ gs) <*> (wanted =<< decode occ w)
diff --git a/src/Plugin/TypeCheck/Nat/Simple/TypeCheckWith.hs b/src/Plugin/TypeCheck/Nat/Simple/TypeCheckWith.hs
--- a/src/Plugin/TypeCheck/Nat/Simple/TypeCheckWith.hs
+++ b/src/Plugin/TypeCheck/Nat/Simple/TypeCheckWith.hs
@@ -7,7 +7,7 @@
 
 import GHC.Plugins (
 	Plugin(..), defaultPlugin, Expr(..), mkUnivCo,
-	Outputable, ppr, text )
+	Outputable, ppr, text, (<+>) )
 import GHC.Tc.Plugin (TcPluginM, tcPluginTrace)
 import GHC.Tc.Types (TcPlugin(..), TcPluginResult(..))
 import GHC.Tc.Types.Constraint (Ct)
@@ -35,6 +35,9 @@
 solve hd ck gs ds ws = do
 	occ <- lookupOrdCondCompare
 	let	(rs, lgs) = gatherSuccess $ result hd (ck occ) gs ds <$> ws
+	tcPluginTrace hd $ "given:" <+> ppr gs
+	tcPluginTrace hd $ "derived:" <+> ppr ds
+	tcPluginTrace hd $ "wanted:" <+> ppr ws
 	TcPluginOk rs [] <$ tcPluginTrace hd (ppr lgs)
 
 result :: (Monoid s, IsSDoc e) =>
diff --git a/test/log.hs b/test/log.hs
--- a/test/log.hs
+++ b/test/log.hs
@@ -1,5 +1,6 @@
 {-# LANGUAGE DataKinds, TypeOperators #-}
 {-# LANGUAGE GADTs #-}
+{-# LANGUAGE AllowAmbiguousTypes #-}
 {-# OPTIONS_GHC -Wall -fno-warn-tabs -fplugin=Plugin.TypeCheck.Nat.Simple #-}
 
 import GHC.TypeNats
@@ -7,6 +8,15 @@
 
 foo :: 1 <= n => Proxy (n - 1 + 1) -> Proxy (n + 1 - 1)
 foo = id
+
+bar :: 1 <= a => Proxy (a + 1 - 1) -> Proxy (a - 1 + 1)
+bar = id
+
+baz :: 1 <= b => Proxy (a + b) -> Proxy ((a + 1) + (b - 1))
+baz = id
+
+hoge :: Proxy (a - 1) -> Proxy (a - 1)
+hoge = id
 
 main :: IO ()
 main = putStrLn "test log"
diff --git a/typecheck-plugin-nat-simple.cabal b/typecheck-plugin-nat-simple.cabal
--- a/typecheck-plugin-nat-simple.cabal
+++ b/typecheck-plugin-nat-simple.cabal
@@ -4,10 +4,10 @@
 --
 -- see: https://github.com/sol/hpack
 --
--- hash: 9d3e7b7255f2ce97474e8b3dbff13024a62015ddc7be0b9dd257e53422ce1268
+-- hash: 7c7a77c61a65eb7d1ae7ea587abd73eedd98ba5f304d8c1af71be691bfc1810b
 
 name:           typecheck-plugin-nat-simple
-version:        0.1.0.6
+version:        0.1.0.7
 synopsis:       Simple type check plugin which calculate addition, subtraction and less-or-equal-than
 description:    Please see the README on GitHub at <https://github.com/YoshikuniJujo/typecheck-plugin-nat-simple#readme>
 category:       Compiler Plugin