type specifier '(simple-vector n) in defmethod

Hi

I am trying to use '(simple-vector n) as type specifier in defmethod but it
is not possible, is there another way?

(typep #(1 2 3 4) '(simple-vector 4))

(defmethod mul ((n fixnum) (m1 (simple-vector n)) (m2 (simple-vector n)))
  (let ((r (make-array (list n))))
    (dotimes (i n)
      (setf (svref r i) (* (svref m1 i) (svref m2 i))))
    r))

Kind regards
Taoufik Dachraoui