diff --git a/QuickCheck.cabal b/QuickCheck.cabal
--- a/QuickCheck.cabal
+++ b/QuickCheck.cabal
@@ -1,5 +1,5 @@
 Name: QuickCheck
-Version: 2.3.0.1
+Version: 2.3.0.2
 Cabal-Version: >= 1.2
 Build-type: Simple
 License: BSD3
diff --git a/Test/QuickCheck/Function.hs b/Test/QuickCheck/Function.hs
--- a/Test/QuickCheck/Function.hs
+++ b/Test/QuickCheck/Function.hs
@@ -206,6 +206,7 @@
   [ p' .+. q  | p' <- shrinkFun shr p ] ++
   [ p  .+. q' | q' <- shrinkFun shr q ]
  where
+  isNil :: (a :-> b) -> Bool
   isNil Nil = True
   isNil _   = False