[plt-scheme] free variable and late binding in Dromadery

It seems that Dromadery's variable/value association system is the same that in DrSCheme:

In Dromadery :
let x = 1;;
let f(y) = x+y;;
let x = 2;;
f(0);;
--> 2

In DrScheme:
(define x 1)
(define (f y) (+ x y))
(define x 2)
(f 0)
--> 2

And finally in Caml (camllight)
let x = 1;;
let f(y) = x+y;;
let x = 2;;
f(0);;
--> 1 !!!!!!!!!

Is Dromadery result a bug or a functionnality ? :))

Pierre