diff --git a/Text/OPML/Lens.hs b/Text/OPML/Lens.hs
--- a/Text/OPML/Lens.hs
+++ b/Text/OPML/Lens.hs
@@ -1,7 +1,7 @@
 {-# OPTIONS_GHC -fno-warn-missing-signatures #-}
 {-# LANGUAGE RankNTypes      #-}
 {-# LANGUAGE TemplateHaskell #-}
-module Text.OPML.Lens where
+module Text.OPML.Lens (module Text.OPML.Lens) where
 
 -- {{{ Imports
 import           Lens.Simple
@@ -34,7 +34,7 @@
   ] ''OpmlHead
 
 expansionStateL :: Traversal' OpmlHead Int
-expansionStateL inj a@OpmlHead { expansionState = es } = (\x -> a { expansionState = x }) <$> sequenceA (map inj es)
+expansionStateL inj a@OpmlHead { expansionState = es } = (\x -> a { expansionState = x }) <$> traverse inj es
 {-# INLINE expansionStateL #-}
 
 -- * 'OutlineSubscription' lenses
diff --git a/Text/OPML/Types.hs b/Text/OPML/Types.hs
--- a/Text/OPML/Types.hs
+++ b/Text/OPML/Types.hs
@@ -1,7 +1,6 @@
 {-# LANGUAGE DeriveGeneric         #-}
 {-# LANGUAGE FlexibleInstances     #-}
 {-# LANGUAGE MultiParamTypeClasses #-}
-{-# LANGUAGE OverloadedStrings     #-}
 {-# LANGUAGE StandaloneDeriving    #-}
 -- | OPML is an XML format for outlines.
 --
diff --git a/opml-conduit.cabal b/opml-conduit.cabal
--- a/opml-conduit.cabal
+++ b/opml-conduit.cabal
@@ -1,5 +1,5 @@
 name:                opml-conduit
-version:             0.6.0.2
+version:             0.6.0.3
 synopsis:            Streaming parser/renderer for the OPML 2.0 format.
 description:
     This library implements the OPML 2.0 standard (<http://dev.opml.org/spec2.html>) as a 'conduit' parser/renderer.
diff --git a/test/Arbitrary.hs b/test/Arbitrary.hs
--- a/test/Arbitrary.hs
+++ b/test/Arbitrary.hs
@@ -7,7 +7,7 @@
 {-# LANGUAGE StandaloneDeriving #-}
 -- | External 'Arbitrary' instances used by OPML types.
 -- All instances are defined through the 'OpmlGen' wrapper to avoid conflicts.
-module Arbitrary where
+module Arbitrary (module Arbitrary) where
 
 -- {{{ Imports
 import           Data.ByteString           (ByteString)