Incorrect value computed (from random tester)

[Paul F. Dietz]

(defun f218 ()
  (bug218 0))

(defun fn218 () 0)
(declaim (notinline fn218))

(defun bug218 (b)
  (unless (position b #(3) :test '<)
    (let ((v9 (fn218)))
      (if (<= -3483114449144072959 v9)
          0
          (if (>= -3483114449144072959 v9)
              144115188075855870
              (labels ((%f14 (&key (key1 v9)) key1))
                (%f14)))))))

(f218) ==> 3 ; should be NIL

x86-64, "2.3.7.125-1490e5f4f"