diff --git a/compiler/lib/build_info.ml b/compiler/lib/build_info.ml
index df09835ca..3d723a5c3 100644
--- a/compiler/lib/build_info.ml
+++ b/compiler/lib/build_info.ml
@@ -90,19 +90,9 @@ let parse s =
       in
       Some t
 
-let to_sexp info =
-  Sexp.List
-    (info
-    |> StringMap.bindings
-    |> List.map ~f:(fun (k, v) -> Sexp.List [ Atom k; Atom v ]))
-
-let from_sexp info =
-  let open Sexp.Util in
-  info
-  |> assoc
-  |> List.fold_left
-       ~f:(fun m (k, v) -> StringMap.add k (single string v) m)
-       ~init:StringMap.empty
+let to_map : t -> string StringMap.t = Fun.id
+
+let of_map : string StringMap.t -> t = Fun.id
 
 exception
   Incompatible_build_info of
diff --git a/compiler/lib/build_info.mli b/compiler/lib/build_info.mli
index 34c72abbc..f80eee164 100644
--- a/compiler/lib/build_info.mli
+++ b/compiler/lib/build_info.mli
@@ -34,9 +34,9 @@ val to_string : t -> string
 
 val parse : string -> t option
 
-val to_sexp : t -> Sexp.t
+val to_map : t -> string StringMap.t
 
-val from_sexp : Sexp.t -> t
+val of_map : string StringMap.t -> t
 
 val with_kind : t -> kind -> t
 
diff --git a/compiler/lib/unit_info.ml b/compiler/lib/unit_info.ml
index 6daa29e73..bcc168a56 100644
--- a/compiler/lib/unit_info.ml
+++ b/compiler/lib/unit_info.ml
@@ -149,43 +149,3 @@ let parse acc s =
       | Some ("Effects_without_cps", b) ->
           Some { acc with effects_without_cps = bool_of_string (String.trim b) }
       | Some (_, _) -> None)
-
-let to_sexp t =
-  let add nm skip v rem = if skip then rem else Sexp.List (Atom nm :: v) :: rem in
-  let set nm f rem =
-    add
-      nm
-      (List.equal ~eq:String.equal (f empty) (f t))
-      (List.map ~f:(fun x -> Sexp.Atom x) (f t))
-      rem
-  in
-  let bool nm f rem =
-    add
-      nm
-      (Bool.equal (f empty) (f t))
-      (if f t then [ Atom "true" ] else [ Atom "false" ])
-      rem
-  in
-  []
-  |> bool "effects_without_cps" (fun t -> t.effects_without_cps)
-  |> set "primitives" (fun t -> t.primitives)
-  |> bool "force_link" (fun t -> t.force_link)
-  |> set "requires" (fun t -> StringSet.elements t.requires)
-  |> add "provides" false [ Atom (StringSet.choose t.provides) ]
-
-let from_sexp t =
-  let open Sexp.Util in
-  let opt_list l = l |> Option.map ~f:(List.map ~f:string) in
-  let list default l = Option.value ~default (opt_list l) in
-  let set default l =
-    Option.value ~default (Option.map ~f:StringSet.of_list (opt_list l))
-  in
-  let bool default v = Option.value ~default (Option.map ~f:(single bool) v) in
-  { provides = t |> member "provides" |> mandatory (single string) |> StringSet.singleton
-  ; requires = t |> member "requires" |> set empty.requires
-  ; primitives = t |> member "primitives" |> list empty.primitives
-  ; force_link = t |> member "force_link" |> bool empty.force_link
-  ; effects_without_cps =
-      t |> member "effects_without_cps" |> bool empty.effects_without_cps
-  ; crcs = StringMap.empty
-  }
diff --git a/compiler/lib/unit_info.mli b/compiler/lib/unit_info.mli
index cd0895fa9..1899b5657 100644
--- a/compiler/lib/unit_info.mli
+++ b/compiler/lib/unit_info.mli
@@ -41,7 +41,3 @@ val prefix : string
 val to_string : t -> string
 
 val parse : t -> string -> t option
-
-val to_sexp : t -> Sexp.t list
-
-val from_sexp : Sexp.t -> t
diff --git a/compiler/lib/sexp.ml b/compiler/lib/wasm/sexp.ml
similarity index 100%
rename from compiler/lib/sexp.ml
rename to compiler/lib/wasm/sexp.ml
diff --git a/compiler/lib/sexp.mli b/compiler/lib/wasm/sexp.mli
similarity index 100%
rename from compiler/lib/sexp.mli
rename to compiler/lib/wasm/sexp.mli
diff --git a/compiler/lib/wasm/wa_link.ml b/compiler/lib/wasm/wa_link.ml
index 93aa9d82f..453c65858 100644
--- a/compiler/lib/wasm/wa_link.ml
+++ b/compiler/lib/wasm/wa_link.ml
@@ -20,6 +20,82 @@ open Stdlib
 
 let times = Debug.find "times"
 
+module Build_info : sig
+  include module type of Build_info
+
+  val to_sexp : t -> Sexp.t
+
+  val from_sexp : Sexp.t -> t
+end = struct
+  include Build_info
+
+  let to_sexp info =
+    Sexp.List
+      (info
+      |> to_map
+      |> StringMap.bindings
+      |> List.map ~f:(fun (k, v) -> Sexp.List [ Atom k; Atom v ]))
+
+  let from_sexp info =
+    let open Sexp.Util in
+    info
+    |> assoc
+    |> List.fold_left
+         ~f:(fun m (k, v) -> StringMap.add k (single string v) m)
+         ~init:StringMap.empty
+    |> of_map
+end
+
+module Unit_info : sig
+  include module type of Unit_info
+
+  val to_sexp : t -> Sexp.t list
+
+  val from_sexp : Sexp.t -> t
+end = struct
+  include Unit_info
+
+  let to_sexp t =
+    let add nm skip v rem = if skip then rem else Sexp.List (Atom nm :: v) :: rem in
+    let set nm f rem =
+      add
+        nm
+        (List.equal ~eq:String.equal (f empty) (f t))
+        (List.map ~f:(fun x -> Sexp.Atom x) (f t))
+        rem
+    in
+    let bool nm f rem =
+      add
+        nm
+        (Bool.equal (f empty) (f t))
+        (if f t then [ Atom "true" ] else [ Atom "false" ])
+        rem
+    in
+    []
+    |> bool "effects_without_cps" (fun t -> t.effects_without_cps)
+    |> set "primitives" (fun t -> t.primitives)
+    |> bool "force_link" (fun t -> t.force_link)
+    |> set "requires" (fun t -> StringSet.elements t.requires)
+    |> add "provides" false [ Atom (StringSet.choose t.provides) ]
+
+  let from_sexp t =
+    let open Sexp.Util in
+    let opt_list l = l |> Option.map ~f:(List.map ~f:string) in
+    let list default l = Option.value ~default (opt_list l) in
+    let set default l =
+      Option.value ~default (Option.map ~f:StringSet.of_list (opt_list l))
+    in
+    let bool default v = Option.value ~default (Option.map ~f:(single bool) v) in
+    { provides = t |> member "provides" |> mandatory (single string) |> StringSet.singleton
+    ; requires = t |> member "requires" |> set empty.requires
+    ; primitives = t |> member "primitives" |> list empty.primitives
+    ; force_link = t |> member "force_link" |> bool empty.force_link
+    ; effects_without_cps =
+        t |> member "effects_without_cps" |> bool empty.effects_without_cps
+    ; crcs = StringMap.empty
+    }
+end
+
 module Wasm_binary = struct
   let header = "\000asm\001\000\000\000"