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diff --git a/testsuite/tests/rename/should_fail/rnfail026.hs b/testsuite/tests/rename/should_fail/rnfail026.hs
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+++ b/testsuite/tests/rename/should_fail/rnfail026.hs
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+{-# LANGUAGE Rank2Types, FlexibleInstances #-}
+
+-- This one made ghc-4.08 crash 
+-- rename/RnEnv.lhs:239: Non-exhaustive patterns in function get_tycon_key
+-- The type in the Monad instance is utterly bogus, of course
+
+module ShouldCompile ( Set ) where
+
+
+data Set a = Set [a]
+       deriving (Eq, Ord, Read, Show)
+
+instance Functor Set where
+        f `fmap` (Set xs) = Set $ f `fmap` xs
+
+instance Monad (forall a. Eq a => Set a) where
+        return x = Set [x]
+
+instance Eq (forall a. [a]) where