diff --git a/ocaml/MO_label.ml b/ocaml/MO_label.ml
index e23b2542..9396668e 100644
--- a/ocaml/MO_label.ml
+++ b/ocaml/MO_label.ml
@@ -6,6 +6,7 @@ type t =
 | Natural
 | Localized
 | Orthonormalized
+| MCSCF
 | None
 [@@deriving sexp]
 
@@ -16,6 +17,7 @@ let to_string = function
   | Orthonormalized -> "Orthonormalized"
   | Natural   -> "Natural"
   | Localized -> "Localized"
+  | MCSCF -> "MCSCF"
   | None      -> "None"
 ;;
 
@@ -26,7 +28,8 @@ let of_string  s =
   | "natural"   -> Natural
   | "localized" -> Localized
   | "orthonormalized" -> Orthonormalized
+  | "mcscf" -> MCSCF
   | "none"      -> None
   | _ -> (print_endline s ; failwith "MO_label should be one of:
-Guess | Orthonormalized | Canonical | Natural | Localized | None.")
+Guess | Orthonormalized | Canonical | Natural | Localized | MCSCF | None.")
 ;;