According to the manual [1], this snippet:

(letrec ((a 42)
         (b (+ a 10)))
  (* a b))

should return "Error: unbound variable: a."  But it returns 2184 in
Guile 2.0.7.  Either there is a bug in the manual or 'letrec' doesn't
work properly.

[1] https://gnu.org/software/guile/manual/guile.html#Local-Bindings