GHC optimisation flag ignored when importing a local module with derived type classes

Given Foo.hs and Bar.hs:

module Foo where
data Food = Food -- deriving Eq

{-# OPTIONS_GHC -O2 -ddump-simpl #-}
module Bar where
import Foo
bar :: Int -> Bool
bar x = x == 72

If I run:

ghc --make Bar -fforce-recomp

I get (snipped):

Bar.bar =
  \ (x_afk :: GHC.Types.Int) ->
    case x_afk of _ { GHC.Types.I# x1_alo ->
    case x1_alo of _ {
      __DEFAULT -> GHC.Types.False;
      72 -> GHC.Types.True
    }
    }

bar now looks pretty well optimised. However, if I uncomment the deriving Eq I get:

Bar.bar1 = GHC.Types.I# 72
Bar.bar2 = GHC.Classes.== @ GHC.Types.Int GHC.Classes.$fEqInt
Bar.bar = \ (x_amD :: GHC.Types.Int) -> Bar.bar2 x_amD Bar.bar1

Now bar looks like terrible code, using dictionaries, boxing etc. It seems adding deriving in the imported and unused module makes it ignore the optimisation level.