diff --git a/distributed-closure.cabal b/distributed-closure.cabal
--- a/distributed-closure.cabal
+++ b/distributed-closure.cabal
@@ -1,5 +1,5 @@
 name:                distributed-closure
-version:             0.4.1
+version:             0.4.1.1
 synopsis:            Serializable closures for distributed programming.
 description:         See README.
 homepage:            https://github.com/tweag/distributed-closure
diff --git a/tests/test.hs b/tests/test.hs
--- a/tests/test.hs
+++ b/tests/test.hs
@@ -6,6 +6,7 @@
 {-# LANGUAGE TemplateHaskell #-}
 {-# LANGUAGE TypeApplications #-}
 {-# LANGUAGE TypeFamilies #-}
+{-# LANGUAGE UndecidableInstances #-}
 
 {-# OPTIONS_GHC -fno-warn-orphans #-}