stepper + big bang broken since 2014, sigh.

Shriram points out that the stepper is broken on this simplest big-bang program:

(require 2htdp/image)
(require 2htdp/universe)
(define (f2 w) (text "hi" 30 "red"))
(big-bang "dummy" [to-draw f2])

Specifically, it produces the error

skip-step?: contract violation
  expected: (or/c (listof procedure?) #f)
  given: (cons (lambda () ...) (cons "supposed to be skipped" (cons (lambda () ...) empty)))
  in: (->
       (or/c
        'normal-break
        'normal-break/values
        'result-exp-break
        'result-value-break
        'double-break
        'late-let-break
        'expr-finished-break
        'define-struct-break)
       (or/c (listof procedure?) #f)
       render-settings?
       boolean?)
  contract from: 
      <pkgs>/htdp-lib/stepper/private/reconstruct.rkt
  blaming: <pkgs>/htdp-lib/stepper/private/model.rkt
   (assuming the contract is correct)
  at: <pkgs>/htdp-lib/stepper/private/reconstruct.rkt:46.2

... in racket 6.1.1, and an essentially equivalent error in all more recent versions.