weaker kind-inference in ghc 7.4.1

Kind.hs

{-# LANGUAGE ScopedTypeVariables, KindSignatures #-}
import Data.Typeable

innerTypeOf :: Typeable a => t a -> TypeRep
innerTypeOf (x :: t a) = typeOf (undefined :: a) -- fail

-- giving a kind explicitly will do
-- innerTypeOf (x :: t (a:: *)) = typeOf (undefined :: a) -- ok


main = print (innerTypeOf ([1]::[Int])) -- print 'Int'

{- 
$ ghc --version
The Glorious Glasgow Haskell Compilation System, version 7.4.1

$ ghc --make Kind.hs
[1 of 1] Compiling Main             ( Kind.hs, Kind.o )

Kind.hs:5:34:
    Expecting an ordinary type, but found a type of kind k_agq
    In an expression type signature: a
    In the first argument of `typeOf', namely `(undefined :: a)'
    In the expression: typeOf (undefined :: a)
-}