[racket] interaction between (require racket) and check-expect

Hi --

My students noticed that certain check-expect tests stop working in the presence of (require racket). For example, the check-expect in this three-line file fails under ISλ:

(require racket)
(define-struct foo (x))
(check-expect (make-foo 0) (make-foo 0))

Why is this happening?

Thanks -- Adam
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