diff --git a/equal-files.cabal b/equal-files.cabal
--- a/equal-files.cabal
+++ b/equal-files.cabal
@@ -1,5 +1,5 @@
 Name:           equal-files
-Version:        0.0.1
+Version:        0.0.2
 License:        GPL
 License-File:   LICENSE
 Author:         Henning Thielemann <haskell@henning-thielemann.de>
@@ -40,6 +40,9 @@
    description: Choose the new smaller, split-up base package.
 
 Executable equal-files
+  Build-Depends:
+    bytestring >= 0.9 && <0.10
+
   If flag(splitBase)
     Build-Depends:
       base >= 3
diff --git a/src/EqualFiles.hs b/src/EqualFiles.hs
--- a/src/EqualFiles.hs
+++ b/src/EqualFiles.hs
@@ -1,6 +1,7 @@
 module Main where
 
 import System.Environment (getArgs, )
+import qualified Data.ByteString as B
 import Data.List (groupBy, sort, intersperse, )
 
 
@@ -15,7 +16,7 @@
 
 clusterEqualFiles :: [FilePath] -> IO [[FilePath]]
 clusterEqualFiles fileNames =
-   do files <- mapM readFile fileNames
+   do files <- mapM B.readFile fileNames
       return (clusterEqualElems (zip files fileNames))
 
 -- output results in a quoted way that might be accessible to further shell scripts