diff --git a/sledge/lib/import/import.ml b/sledge/lib/import/import.ml
index f2111e1ea..7c8e1e5f3 100644
--- a/sledge/lib/import/import.ml
+++ b/sledge/lib/import/import.ml
@@ -12,8 +12,9 @@ include (
     sig
       include
         (module type of Base
+          with module Option := Base.Option
           (* prematurely deprecated, remove and use Stdlib instead *)
-          with module Filename := Base.Filename
+           and module Filename := Base.Filename
            and module Format := Base.Format
            and module Marshal := Base.Marshal
            and module Scanf := Base.Scanf
@@ -131,25 +132,7 @@ let filter_map_preserving_phys_equal filter_map t ~f =
   in
   if !change then t' else t
 
-module Option = struct
-  include Base.Option
-
-  let pp fmt pp_elt fs = function
-    | Some x -> Format.fprintf fs fmt pp_elt x
-    | None -> ()
-
-  let cons xo xs = match xo with Some x -> x :: xs | None -> xs
-
-  module Monad_syntax = struct
-    type nonrec 'a t = 'a t
-
-    let ( let+ ) x f = map ~f x
-    let ( and+ ) x y = both x y
-    let ( let* ) x f = bind ~f x
-    let ( and* ) x y = both x y
-  end
-end
-
+module Option = Option
 include Option.Monad_infix
 include Option.Monad_syntax
 
diff --git a/sledge/lib/import/import.mli b/sledge/lib/import/import.mli
index 0609a4f20..a5a9afed4 100644
--- a/sledge/lib/import/import.mli
+++ b/sledge/lib/import/import.mli
@@ -12,8 +12,9 @@ include module type of (
     sig
       include
         (module type of Base
+          with module Option := Base.Option
           (* prematurely deprecated, remove and use Stdlib instead *)
-          with module Filename := Base.Filename
+           and module Filename := Base.Filename
            and module Format := Base.Format
            and module Marshal := Base.Marshal
            and module Scanf := Base.Scanf
@@ -102,18 +103,7 @@ val or_error : ('a -> 'b) -> 'a -> unit -> 'b or_error
 (** Extensions *)
 
 module Invariant : module type of Base.Invariant
-
-module Option : sig
-  include module type of Base.Option
-
-  val pp : ('a_pp -> 'a -> unit, unit) fmt -> 'a_pp -> 'a option pp
-  (** Pretty-print an option. *)
-
-  val cons : 'a t -> 'a list -> 'a list
-
-  module Monad_syntax : Monad_syntax
-end
-
+module Option = Option
 include module type of Option.Monad_infix
 include module type of Option.Monad_syntax with type 'a t = 'a option
 
diff --git a/sledge/lib/import/option.ml b/sledge/lib/import/option.ml
new file mode 100644
index 000000000..ffa0bd68f
--- /dev/null
+++ b/sledge/lib/import/option.ml
@@ -0,0 +1,27 @@
+(*
+ * Copyright (c) Facebook, Inc. and its affiliates.
+ *
+ * This source code is licensed under the MIT license found in the
+ * LICENSE file in the root directory of this source tree.
+ *)
+
+open (
+  Base :
+    (module type of Base with module Format := Base.Format [@warning "-3"]) )
+
+include Base.Option
+
+let pp fmt pp_elt fs = function
+  | Some x -> Format.fprintf fs fmt pp_elt x
+  | None -> ()
+
+let cons xo xs = match xo with Some x -> x :: xs | None -> xs
+
+module Monad_syntax = struct
+  type nonrec 'a t = 'a t
+
+  let ( let+ ) x f = map ~f x
+  let ( and+ ) x y = both x y
+  let ( let* ) x f = bind ~f x
+  let ( and* ) x y = both x y
+end
diff --git a/sledge/lib/import/option.mli b/sledge/lib/import/option.mli
new file mode 100644
index 000000000..ac2eb9d2c
--- /dev/null
+++ b/sledge/lib/import/option.mli
@@ -0,0 +1,17 @@
+(*
+ * Copyright (c) Facebook, Inc. and its affiliates.
+ *
+ * This source code is licensed under the MIT license found in the
+ * LICENSE file in the root directory of this source tree.
+ *)
+
+open Base
+open Import0
+include module type of Base.Option
+
+val pp : ('a_pp -> 'a -> unit, unit) fmt -> 'a_pp -> 'a option pp
+(** Pretty-print an option. *)
+
+val cons : 'a t -> 'a list -> 'a list
+
+module Monad_syntax : Monad_syntax with type 'a t = 'a option