diff --git a/src/stdune/sexp.ml b/src/stdune/sexp.ml
index f6576565..2f31ed7a 100644
--- a/src/stdune/sexp.ml
+++ b/src/stdune/sexp.ml
@@ -141,6 +141,14 @@ module Of_sexp = struct
       | Fields (loc, cstr, uc) ->
         t (Fields (loc, cstr, Univ_map.add uc key v)) state
 
+  let set_many : type a k. Univ_map.t -> (a, k) parser -> (a, k) parser
+    = fun map t ctx state ->
+      match ctx with
+      | Values (loc, cstr, uc) ->
+        t (Values (loc, cstr, Univ_map.superpose uc map)) state
+      | Fields (loc, cstr, uc) ->
+        t (Fields (loc, cstr, Univ_map.superpose uc map)) state
+
   let loc : type k. k context -> k -> Loc.t * k = fun ctx state ->
     match ctx with
     | Values (loc, _, _) -> (loc, state)
diff --git a/src/stdune/sexp.mli b/src/stdune/sexp.mli
index 360acdaa..095c1e1f 100644
--- a/src/stdune/sexp.mli
+++ b/src/stdune/sexp.mli
@@ -109,6 +109,7 @@ module Of_sexp : sig
   (** Access to the context *)
   val get : 'a Univ_map.Key.t -> ('a option, _) parser
   val set : 'a Univ_map.Key.t -> 'a -> ('b, 'k) parser -> ('b, 'k) parser
+  val set_many : Univ_map.t -> ('a, 'k) parser -> ('a, 'k) parser
 
   (** Return the location of the list currently being parsed. *)
   val loc : (Loc.t, _) parser