incorrect results when not compiling with optimisation

This is a cut-down random1283.

R.hs:

module R (randomIO) where

class Num a => Random a where
    randomIO :: IO a

instance Random Int where
    randomIO = return 10003

s.hs:

import R

main :: IO ()
main = do r >>= print
          r >>= print

r :: IO Int
r = randomIO

$ rm *.o *.hi s
$ ghc -c R.hs
$ ghc s.hs R.o -o s
$ ./s
-4611686018427387865
-4611686018427387865
$ rm *.o *.hi s
$ ghc -c R.hs
$ ghc s.hs R.o -o s -O
$ ./s
10003
10003
$ ghc --version
The Glorious Glasgow Haskell Compilation System, version 6.11.20081205

Trac metadata

Trac field	Value
Version	6.11
Type	Bug
TypeOfFailure	OtherFailure
Priority	high
Resolution	Unresolved
Component	Compiler
Test case
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