`INLINE` pragma on where clause ignored by GHC

In this program GHC decides to ingore the INLINE pragma:

module M (foo) where

import Prelude hiding ( succ )
import qualified Prelude as Prelude

succ :: Enum e => e -> e
succ !x = Prelude.succ x

{-# NOINLINE foo #-}
foo :: (Num e, Enum e) => Bool -> e -> e
foo b x =
    if b
        then succ $ large x
        else large x
    where
    {-# INLINE large #-}
    large x = succ . succ . succ . succ . succ . succ . succ . succ . succ . succ . succ . succ . succ . succ . succ . succ . succ . succ . succ . succ . succ . succ . succ . succ . succ . succ . succ
            . succ . succ . succ . succ . succ . succ . succ . succ . succ . succ . succ . succ . succ . succ . succ . succ . succ . succ . succ . succ . succ . succ . succ . succ . succ . succ . succ $ x

If I move large to the top level or give the local version a type signature it get's inlined as expected.

To me this is very surprising behavior. I reproduced this with a fairly recent master and 9.6.2 when using -O.