diff --git a/crypto-random-effect.cabal b/crypto-random-effect.cabal
--- a/crypto-random-effect.cabal
+++ b/crypto-random-effect.cabal
@@ -2,7 +2,7 @@
 --  documentation, see http://haskell.org/cabal/users-guide/
 
 name:                crypto-random-effect
-version:             0.2.0.4
+version:             0.2.0.4.1
 synopsis:            A random effect using crypto-random
 description:         Any help (especially documentation) is welcome
 homepage:            https://github.com/ibotty/crypto-random-effect
diff --git a/src/Crypto/Random/Effect.hs b/src/Crypto/Random/Effect.hs
--- a/src/Crypto/Random/Effect.hs
+++ b/src/Crypto/Random/Effect.hs
@@ -32,6 +32,7 @@
 import Control.Eff.Reader.Strict
 import Data.ByteString (ByteString)
 import Data.SecureMem (SecureMem)
+import Data.Typeable (Typeable)
 import Crypto.Random (CPRG, EntropyPool, SystemRNG)
 import qualified Crypto.Random as C