-fallow-incoherent-instances not working

[Marc Weber]

I'm trying to learn more about HList.
While setting up a small test application I got the following error..
ghc(i) tells me to add -fallow-incoherent-instances but doesn't
recognize it ?
Is this a bug?

marc at localhost /pr/haskell/test/HList $ ghci -package HList HListTestMain.hs
   ___         ___ _
  / _ \ /\  /\/ __(_)
 / /_\// /_/ / /  | |      GHC Interactive, version 6.6, for Haskell 98.
/ /_\\/ __  / /___| |      http://www.haskell.org/ghc/
\____/\/ /_/\____/|_|      Type :? for help.

Loading package base ... linking ... done.
Loading package HList-0.1 ... linking ... done.
[1 of 2] Compiling HListTest.HList  ( HListTest/HList.hs, interpreted )

HListTest/HList.hs:12:11:
    Overlapping instances for HOccursMany (Maybe Int)
                                          (HCons t
                                                 (HCons t1 (HCons [Char] (HCons (Maybe t2) HNil))))
      arising from use of `hOccursMany' at HListTest/HList.hs:12:11-24
    Matching instances:
      instance [overlap ok] (HOccursMany e l, HList l) =>
                            HOccursMany e (HCons e' l)
        -- Defined in HOccurs
      instance [overlap ok] (HOccursMany e l, HList l) =>
                            HOccursMany e (HCons e l)
        -- Defined in HOccurs
    (The choice depends on the instantiation of `t, t1, t2'
     Use -fallow-incoherent-instances to use the first choice above)
    In the expression: hOccursMany l1
    In the second argument of `($)', namely
        `(hOccursMany l1 :: [Maybe Int])'
    In the expression: print $ (hOccursMany l1 :: [Maybe Int])
Failed, modules loaded: none.
Prelude> Leaving GHCi.


marc at localhost /pr/haskell/test/HList $ cat HListTest/HList.hs
{-# OPTIONS -fglasgow-exts #-}
{-# OPTIONS -fallow-undecidable-instances #-}
{-# OPTIONS -fallow-overlapping-instances #-}
{-# OPTIONS -fallow-incoherent-instances #-} -- <<<<<<<<<<<< given here
module HListTest.HList where
import HList

l1 = 2 .*. 3 .*. "abc" .*. (Just 4) .*. HNil

hlistTest = do
  print $ 2 .*. HNil
  print $ (hOccursMany l1 :: [Maybe Int])
marc at localhost /pr/haskell/test/HList $


Marc