diff --git a/lgtk.cabal b/lgtk.cabal
--- a/lgtk.cabal
+++ b/lgtk.cabal
@@ -1,5 +1,5 @@
 name:               lgtk
-version:            0.1.0.1
+version:            0.1.0.2
 category:           GUI
 synopsis:           lens-based GUI with Gtk backend
 description:
diff --git a/src/Control/MLens/ExtRef/Pure.hs b/src/Control/MLens/ExtRef/Pure.hs
--- a/src/Control/MLens/ExtRef/Pure.hs
+++ b/src/Control/MLens/ExtRef/Pure.hs
@@ -4,7 +4,7 @@
 {- |
 Pure reference implementation for the @ExtRef@ interface.
 
-The implementation use @unsafeCoerce@ internally, but its effect cannot escape.
+The implementation uses @unsafeCoerce@ internally, but its effect cannot escape.
 -}
 module Control.MLens.ExtRef.Pure
     ( Ext, runExt, runExt_
diff --git a/src/Data/MLens.hs b/src/Data/MLens.hs
--- a/src/Data/MLens.hs
+++ b/src/Data/MLens.hs
@@ -65,7 +65,7 @@
 
 TODO: List laws, document which laws hold for each lenses.
 -}
-data MLens m a b
+newtype MLens m a b
     = MLens (a -> m (b, b -> m a))
 
 {-|
diff --git a/src/GUI/MLens/Gtk/Demos/TEditor.hs b/src/GUI/MLens/Gtk/Demos/TEditor.hs
--- a/src/GUI/MLens/Gtk/Demos/TEditor.hs
+++ b/src/GUI/MLens/Gtk/Demos/TEditor.hs
@@ -1,6 +1,3 @@
---{-# LANGUAGE ExistentialQuantification #-}
---{-# LANGUAGE MultiParamTypeClasses #-}
---{-# LANGUAGE FlexibleInstances #-}
 {-# LANGUAGE GADTs #-}
 {-# LANGUAGE TypeFamilies #-}
 {-# LANGUAGE DataKinds #-}