Cannot parse the unit value in refinement bounds

I'm not really sure it's by design or not, LH fails to parse bounds which include the unit literal ().

{-@
    testee :: forall <
                p :: Int -> () -> Int -> Bool
              , q :: Int -> () -> Int -> Bool
              >.
              { n :: Int |- Int<p n ()> <: Int<q n ()> }
              Int
@-}
testee :: Int
testee = 42

Literals of the types other than () look okay, e.g. in the case of Int or Bool, the code is compilable.

{-@
    testee :: forall <
                p :: Int -> Int -> Int -> Bool
              , q :: Int -> Int -> Int -> Bool
              >.
              { n :: Int |- Int<p n 42> <: Int<q n 42> }
              Int
@-}
testee :: Int
testee = 42