compiler bug (LWw)

Hello,

The execution of the following compiled function

(defun test ()
  (declare (optimize (safety 1)))
  (let ((str (make-string 1)))
    (setf (schar str 0) #\Space)
    str))

gives an error if safety is declared to be 1. And no error with any other value of safety (LWw).

USER 27 > (test)

Error: #\Space is not of type base-char.
  1 (abort) Return to level 0.
  2 Return to top loop level 0.

Regards,

Francis