Panic on standlone deriving without GeneralizedNewtypeDeriving

I found that GHC panics on the following program if GeneralizedNewtypeDeriving pragma is removed. Otherwise it works just fine.

{-# LANGUAGE StandaloneDeriving #-}
{-# LANGUAGE GeneralizedNewtypeDeriving #-} -- Removal causes crash
import Data.Monoid

newtype DecodeMap e = DecodeMap [e]

deriving instance Monoid (DecodeMap e)

Here is error message it produce

ghc: panic! (the 'impossible' happened)
  (GHC version 6.12.1 for i386-unknown-linux):
        genDerivBinds: bad derived class base:Data.Monoid.Monoid{tc rha}

Please report this as a GHC bug:  http://www.haskell.org/ghc/reportabug

This bug appears only in GHC6.12.1. GHC6.10.4 rightfully complain that I should enable GeneralizedNewtypeDeriving unstead of crashing.

Trac metadata

Trac field	Value
Version	6.12.1
Type	Bug
TypeOfFailure	OtherFailure
Priority	normal
Resolution	Unresolved
Component	Compiler
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