diff --git a/byg/byg.cabal b/byg/byg.cabal
index 9f7199e..79f4032 100644
--- a/byg/byg.cabal
+++ b/byg/byg.cabal
@@ -20,3 +20,4 @@ executable byg
     build-depends:
         base
       , mtl
+      , bytestring
diff --git a/byg/src/Main.hs b/byg/src/Main.hs
index 71d7466..6895dbf 100644
--- a/byg/src/Main.hs
+++ b/byg/src/Main.hs
@@ -6,6 +6,7 @@ module Main where
 import Unsafe.Coerce (unsafeCoerce)
 import Control.Monad.State
 import Control.Monad.Writer
+import Data.ByteString (ByteString)
 
 data Source a where
   -- Void :: Source ()