Incorrect result from POSITION on list with characters

[Paul F. Dietz]

(defun f377 (p1)
  (declare (optimize (speed 2) (safety 0) (debug 2) (space 3))
                      (type (member nreverse #\U7BFA #\w) p1))
  (position (the character p1)
            '(#\U7BFA #*0101 #\U7BFA #*0000 #*0111 #\U7BFA
              #\U7BFA)))

(defun bug377 ()
  (f377 #\U7BFA))

(bug377) ==> 6

x86-64, "2.4.3.69-d0fddf39d"