diff --git a/ocaml/MO_class.ml b/ocaml/MO_class.ml
index 9df80240..951d6aed 100644
--- a/ocaml/MO_class.ml
+++ b/ocaml/MO_class.ml
@@ -1,5 +1,6 @@
-open Core
 open Qptypes
+open Sexplib.Std
+
 
 type t =
   | Core     of MO_number.t list
@@ -12,8 +13,8 @@ type t =
 
 let to_string  x =
   let print_list l =
-    let s = List.map ~f:(fun x-> MO_number.to_int x |> string_of_int )l
-            |> (String.concat ~sep:", ")
+    let s = List.map (fun x-> MO_number.to_int x |> string_of_int ) l
+            |> (String.concat ", ")
     in
     "("^s^")"
   in
@@ -42,7 +43,7 @@ let of_string s =
 
 
 let _mo_number_list_of_range range =
-  Range.of_string range |> List.map ~f:MO_number.of_int
+  Range.of_string range |> List.map MO_number.of_int
 
 
 let create_core     range = Core     (_mo_number_list_of_range range)