GHC panics while trying to derive a Generic instance for Complex a

Using the StandaloneDeriving and DeriveGeneric extensions, GHC panics when deriving a Generic instance for Complex a with the following error:

GHCi, version 7.4.1: http://www.haskell.org/ghc/  :? for help
Loading package ghc-prim ... linking ... done.
Loading package integer-gmp ... linking ... done.
Loading package base ... linking ... done.
[1 of 1] Compiling Main             ( TestCase.hs, interpreted )
ghc: panic! (the 'impossible' happened)
  (GHC version 7.4.1 for x86_64-unknown-freebsd):
	tcTyVarDetails
    ( a{tv ahY} [tv] :: ghc-prim:GHC.Prim.*{(w) tc 34d} )