diff --git a/WarcExport.hs b/WarcExport.hs
--- a/WarcExport.hs
+++ b/WarcExport.hs
@@ -1,6 +1,7 @@
 {-# LANGUAGE OverloadedStrings #-}
 
 import Data.List (isSuffixOf)
+import Data.Monoid
 import Control.Applicative
 import System.IO
 import System.FilePath
diff --git a/warc.cabal b/warc.cabal
--- a/warc.cabal
+++ b/warc.cabal
@@ -1,5 +1,5 @@
 name:                warc
-version:             0.3.0
+version:             0.3.1
 synopsis:            A parser for the Web Archive (WARC) format
 description:         A streaming parser for the Web Archive (WARC) format.
 homepage:            http://github.com/bgamari/warc
@@ -42,7 +42,7 @@
                        filepath,
                        exceptions,
                        pipes-zlib,
-                       optparse-applicative,
+                       optparse-applicative >= 0.12 && < 0.14,
                        pipes,
                        attoparsec,
                        bytestring,