Standalone deriving doesn't do newtype deriving properly

I'd expect the following two declarations to have identical behavior:

newtype S1 x y a = S1 (M S x y a) deriving IxMonad

newtype S2 x y a = S2 (M S x y a)
deriving instance IxMonad S2

Results:

$ ghc-6.11.20081005 -c deriving.hs

deriving.hs:15:0:
    Can't make a derived instance of `IxMonad S2'
      (even with cunning newtype deriving:
       the representation type has wrong kind)
    In the stand-alone deriving instance for `IxMonad S2'

Trac metadata

Trac field	Value
Version	6.11
Type	Bug
TypeOfFailure	OtherFailure
Priority	normal
Resolution	Unresolved
Component	Compiler
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