fails to catch ill-typed property values that are partially annotated

[capfredf]

What version of Racket are you using?

7.9.0.10 on c71e6289af3f1c6e4498e3503519d95f889cdcb6

What program did you run?

(struct root ([p : Integer] [q : Integer])
    #:property prop:custom-write 
    (λ ([me : Integer] [port : Output-Port] mode) : Void
         (fprintf port "[[~a ~a]]" (root-p me) (root-q me))))

What should have happened?

A type error

If you got an error message, please include it here.

---

If the parameter mode in the lambda is correctly annotated with (U Boolean 1 0), then the typechecker reports a type error expectedly