GADT internal error on incorrect program

Hi there, is this one known?

andres@adorp trans $ ghc --version
The Glorious Glasgow Haskell Compilation System, version 6.4
andres@adorp trans $ cat > Bug.hs <<EOF
> data RInt a where Int :: RInt
> EOF
andres@adorp trans $ ghc -c -fglasgow-exts EOF.hs     
ghc-6.4: file `EOF.hs' does not exist
andres@adorp trans $ ghc -c -fglasgow-exts Bug.hs
ghc-6.4: panic! (the `impossible' happened, GHC version 6.4):
        types/Type.lhs:(1107,0)-(1108,77): Non-exhaustive patterns in
        function zip_ty_env


Please report it as a compiler bug to
glasgow-haskell-bugs@xxxxxxxxxxx,
or http://sourceforge.net/projects/ghc/.


Best wishes,
  Andres