purescript instance operator behaviour

-- this builds fine:
instance semiMonoid :: Semigroup Multiply where
  append  (Multiply a) (Multiply b) = Multiply (a * b)

-- But this fails with the error **Unexpected token '(<>)' **
instance semiMonoid :: Semigroup Multiply where
  (<>)  (Multiply a) (Multiply b) = Multiply (a * b)