1 files changed, 10 insertions, 1 deletions

diff --git a/lib/iban.ml b/lib/iban.ml
index fbea774..9b516c4 100644
--- a/lib/iban.ml
+++ b/lib/iban.ml
@@ -82,7 +82,16 @@ let to_string = Fn.id
 let of_string s =
   match make s with
   | Some iban -> iban
-  | None -> Printf.failwithf "Iban.of_string: %S" s ()
+  | None -> Printf.failwithf "Iban.of_string: invalid IBAN %S" s ()
 
 let sexp_of_t iban = Sexp.Atom iban
+
+let t_of_sexp sexp =
+  match sexp with
+  | Sexp.Atom s -> (
+      match make s with
+      | Some iban -> iban
+      | None -> of_sexp_error "Iban.t_of_sexp: invalid IBAN" sexp)
+  | Sexp.List _ -> of_sexp_error "Iban.t_of_sexp: expected a list" sexp
+
 let equal = String.equal