Abysmal error message from `ghc -M`

ghc-6.6.1 -M -cpp Foo.hs Bar.hs
/tmp/ghc9234_0/ghc9234_2.hscpp:1:0:
    file name does not match module name `Main'

What a terrible message! The source code is this:

Foo.hs (note the mis-typed Module)

Module Foo where
  f x = x

Bar.hs

module Bar where
  import Foo

Trac metadata

Trac field	Value
Version	6.6.1
Type	Bug
TypeOfFailure	OtherFailure
Priority	normal
Resolution	Unresolved
Component	Compiler
Test case
Differential revisions
BlockedBy
Related
Blocking
CC
Operating system	Unknown
Architecture	Unknown