An example of the documentation doesn't not work (with-solved-problem)

[MathCoursOrg]

What i did ?

I type into a new file these lines :

(ql:quickload :linear-programming)

(use-package :linear-programming)

(with-solved-problem ((max (= w (+ x (* 4 y) (* 3 z))))
                      (<= (+ (* 2 x) y) 8)
                      (<= (+ y z) 7))
  (format t "Objective value solution: ~A~%" w)
  (format t "x = ~A (reduced cost: ~A)~%" x (reduced-cost x))
  (format t "y = ~A (reduced cost: ~A)~%" y (reduced-cost y))
  (format t "z = ~A (reduced cost: ~A)~%" z (reduced-cost z)))

The compilation is ok, but when i eval the with-solved-problem form I encountered this error :

Execution of a form compiled with errors.
Form:
  #S(PROBLEM
   :TYPE MAX
   :VARS #<(SIMPLE-VECTOR 3) {100260C13F}>
   :OBJECTIVE-VAR W
   :OBJECTIVE-FUNC ((Z . 3) (Y . 4) (X . 1))
   :INTEGER-VARS NIL
   :VAR-BOUNDS NIL
   :CONSTRAINTS ((<= ((Y . 1) (X . 2)) 8) (<= ((Z . 1) (Y . 1)) 7)))
Compile-time error:
  don't know how to dump #S(PROBLEM
                          :TYPE MAX
                          :VARS #(X Z Y)
                          :OBJECTIVE-VAR W
                          :OBJECTIVE-FUNC ((Z . 3) (Y . 4) (X . 1))
                          :INTEGER-VARS NIL
                          :VAR-BOUNDS NIL
                          :CONSTRAINTS ((<= ((Y . 1) (X . 2)) 8)
                                        (<= ((Z . 1) (Y . 1)) 7))) (default MAKE-LOAD-FORM method called).
   [Condition of type SB-INT:COMPILED-PROGRAM-ERROR]