(defparameter *h* (make-hash-table :test #'equal))
(defparameter *s* (make-array 10 :fill-pointer 0 :element-type 'character))

(setf (gethash *s* *h*) 1)

(assert (equal "" *s*))
(assert (eql 1 (gethash *s* *h*)))
(assert (eql 1 (gethash "" *h*)))