diff --git a/lib/s.ml b/lib/s.ml
index a7095fe3..de8c353f 100644
--- a/lib/s.ml
+++ b/lib/s.ml
@@ -87,7 +87,7 @@ module type BUILDER = sig
   val build :
     t ->
     context ->
-    Obuilder_spec.stage ->
+    Obuilder_spec.t ->
     (id, [`Cancelled | `Msg of string]) Lwt_result.t
 
   val delete : ?log:(id -> unit) -> t -> id -> unit Lwt.t
diff --git a/lib_spec/docker.mli b/lib_spec/docker.mli
index eec67fb6..572e8468 100644
--- a/lib_spec/docker.mli
+++ b/lib_spec/docker.mli
@@ -1,4 +1,4 @@
-val dockerfile_of_spec : buildkit:bool -> Spec.stage -> Dockerfile.t
+val dockerfile_of_spec : buildkit:bool -> Spec.t -> Dockerfile.t
 (** [dockerfile_of_spec x] produces a Dockerfile that aims to be equivalent to [x].
 
     However, note that:
diff --git a/lib_spec/spec.ml b/lib_spec/spec.ml
index 1ed1c803..fd32c571 100644
--- a/lib_spec/spec.ml
+++ b/lib_spec/spec.ml
@@ -92,19 +92,19 @@ let op_of_sexp x =
     op_of_sexp (List (Atom name :: args))
   | x -> Fmt.failwith "Invalid op: %a" Sexplib.Sexp.pp_hum x
 
-type stage = {
+type t = {
   from : string;
   ops : op list;
 }
 
-let sexp_of_stage { from; ops } =
+let sexp_of_t { from; ops } =
   let open Sexplib.Sexp in
   List (List [ Atom "from"; Atom from ] :: List.map sexp_of_op ops)
 
-let stage_of_sexp = function
+let t_of_sexp = function
   | Sexplib.Sexp.List (List [ Atom "from"; Atom from ] :: ops) ->
     { from; ops = List.map op_of_sexp ops }
-  | x -> Fmt.failwith "Invalid stage: %a" Sexplib.Sexp.pp_hum x
+  | x -> Fmt.failwith "Invalid spec: %a" Sexplib.Sexp.pp_hum x
 
 let comment fmt = fmt |> Printf.ksprintf (fun c -> `Comment c)
 let workdir x = `Workdir x
@@ -135,8 +135,8 @@ let pp_op_sexp f : Sexplib.Sexp.t -> unit = function
       (Fmt.list ~sep:Fmt.sp pp_one_line) args
   | x -> pp_one_line f x
 
-let pp_stage f t =
-  match sexp_of_stage t with
+let pp f t =
+  match sexp_of_t t with
   | List lines ->
     Fmt.pf f "(@[<v>%a@]@,)" (Fmt.list ~sep:Fmt.cut pp_op_sexp) lines
   | x -> Sexplib.Sexp.pp_hum f x
diff --git a/lib_spec/spec.mli b/lib_spec/spec.mli
index 2f3f736a..323a5c8d 100644
--- a/lib_spec/spec.mli
+++ b/lib_spec/spec.mli
@@ -25,12 +25,12 @@ type op = [
   | `Env of (string * string)
 ] [@@deriving sexp]
 
-type stage = {
+type t = {
   from : string;
   ops : op list;
 } [@@deriving sexp]
 
-val stage : from:string -> op list -> stage
+val stage : from:string -> op list -> t
 
 val comment : ('a, unit, string, op) format4 -> 'a
 val workdir : string -> op
@@ -42,8 +42,8 @@ val user : uid:int -> gid:int -> op
 
 val root : user
 
-val pp_stage : stage Fmt.t
-(** [pp_stage f s] is similar to [Sexplib.Sexp.pp_hum f (sexp_of_stage s)], but
+val pp : t Fmt.t
+(** [pp f s] is similar to [Sexplib.Sexp.pp_hum f (sexp_of_t s)], but
     attempts to improve the layout slightly by putting each operation on its
     own line. *)
 
diff --git a/main.ml b/main.ml
index a9dcd114..75e9c210 100644
--- a/main.ml
+++ b/main.ml
@@ -30,7 +30,7 @@ let create_builder ?fast_sync spec =
 let build fast_sync store spec src_dir =
   Lwt_main.run begin
     create_builder ~fast_sync store >>= fun (Builder ((module Builder), builder)) ->
-    let spec = Obuilder.Spec.stage_of_sexp (Sexplib.Sexp.load_sexp spec) in
+    let spec = Obuilder.Spec.t_of_sexp (Sexplib.Sexp.load_sexp spec) in
     let context = Obuilder.Context.v ~log ~src_dir () in
     Builder.build builder context spec >>= function
     | Ok x ->
@@ -52,7 +52,7 @@ let delete store id =
 
 let dockerfile buildkit spec =
   Sexplib.Sexp.load_sexp spec
-  |> Obuilder_spec.stage_of_sexp
+  |> Obuilder_spec.t_of_sexp
   |> Obuilder_spec.Docker.dockerfile_of_spec ~buildkit
   |> Dockerfile.string_of_t
   |> print_endline
diff --git a/stress/stress.ml b/stress/stress.ml
index 8dcc49da..dfbae97e 100644
--- a/stress/stress.ml
+++ b/stress/stress.ml
@@ -133,7 +133,7 @@ module Test(Store : S.STORE) = struct
       |> fun got ->
       assert_str expected got
     in
-    check_log, { Spec.from = "busybox"; ops }
+    check_log, Spec.stage ~from:"busybox" ops
 
   let do_build builder =
     let src_dir = "/root" in
diff --git a/test/test.ml b/test/test.ml
index b76fd108..65301d61 100644
--- a/test/test.ml
+++ b/test/test.ml
@@ -59,7 +59,7 @@ let test_simple _switch () =
   with_config @@ fun ~src_dir ~store ~sandbox ~builder ->
   let log = Log.create "b" in
   let context = Context.v ~src_dir ~log:(Log.add log) () in
-  let spec = Spec.{ from = "base"; ops = [ run "Append" ] } in
+  let spec = Spec.(stage ~from:"base" [ run "Append" ]) in
   Mock_sandbox.expect sandbox (mock_op ~output:(`Append ("runner", "base-id")) ());
   B.build builder context spec >>!= get store "output" >>= fun result ->
   Alcotest.(check build_result) "Final result" (Ok "base-distro\nrunner") result;
@@ -88,7 +88,7 @@ let test_prune _switch () =
   let start = Unix.(gettimeofday () |> gmtime) in
   let log = Log.create "b" in
   let context = Context.v ~src_dir ~log:(Log.add log) () in
-  let spec = Spec.{ from = "base"; ops = [ run "Append" ] } in
+  let spec = Spec.(stage ~from:"base" [ run "Append" ]) in
   Mock_sandbox.expect sandbox (mock_op ~output:(`Append ("runner", "base-id")) ());
   B.build builder context spec >>!= get store "output" >>= fun result ->
   Alcotest.(check build_result) "Final result" (Ok "base-distro\nrunner") result;
@@ -115,8 +115,8 @@ let test_concurrent _switch () =
   let log2 = Log.create "b2" in
   let context1 = Obuilder.Context.v ~log:(Log.add log1) ~src_dir () in
   let context2 = Obuilder.Context.v ~log:(Log.add log2) ~src_dir () in
-  let spec1 = Obuilder.Spec.{ from = "base"; ops = [ run "A"; run "B" ] } in
-  let spec2 = Obuilder.Spec.{ from = "base"; ops = [ run "A"; run "C" ] } in
+  let spec1 = Obuilder.Spec.(stage ~from:"base"[ run "A"; run "B" ]) in
+  let spec2 = Obuilder.Spec.(stage ~from:"base"[ run "A"; run "C" ]) in
   let a, a_done = Lwt.wait () in
   Mock_sandbox.expect sandbox (mock_op ~result:a ~output:(`Constant "A") ());
   Mock_sandbox.expect sandbox (mock_op ~output:`Append_cmd ());
@@ -161,8 +161,8 @@ let test_concurrent_failure _switch () =
   let log2 = Log.create "b2" in
   let context1 = Obuilder.Context.v ~log:(Log.add log1) ~src_dir () in
   let context2 = Obuilder.Context.v ~log:(Log.add log2) ~src_dir () in
-  let spec1 = Obuilder.Spec.{ from = "base"; ops = [ run "A"; run "B" ] } in
-  let spec2 = Obuilder.Spec.{ from = "base"; ops = [ run "A"; run "C" ] } in
+  let spec1 = Obuilder.Spec.(stage ~from:"base" [ run "A"; run "B" ]) in
+  let spec2 = Obuilder.Spec.(stage ~from:"base" [ run "A"; run "C" ]) in
   let a, a_done = Lwt.wait () in
   Mock_sandbox.expect sandbox (mock_op ~result:a ());
   let b1 = B.build builder context1 spec1 in
@@ -198,8 +198,8 @@ let test_concurrent_failure_2 _switch () =
   let log2 = Log.create "b2" in
   let context1 = Obuilder.Context.v ~log:(Log.add log1) ~src_dir () in
   let context2 = Obuilder.Context.v ~log:(Log.add log2) ~src_dir () in
-  let spec1 = Obuilder.Spec.{ from = "base"; ops = [ run "A"; run "B" ] } in
-  let spec2 = Obuilder.Spec.{ from = "base"; ops = [ run "A"; run "C" ] } in
+  let spec1 = Obuilder.Spec.(stage ~from:"base" [ run "A"; run "B" ]) in
+  let spec2 = Obuilder.Spec.(stage ~from:"base" [ run "A"; run "C" ]) in
   let a, a_done = Lwt.wait () in
   Mock_sandbox.expect sandbox (mock_op ~result:(Lwt_result.fail (`Msg "Mock build failure")) ~delay_store:a ());
   let b1 = B.build builder context1 spec1 in
@@ -232,7 +232,7 @@ let test_cancel _switch () =
   let log = Log.create "b" in
   let switch = Lwt_switch.create () in
   let context = Context.v ~switch ~src_dir ~log:(Log.add log) () in
-  let spec = Spec.{ from = "base"; ops = [ run "Wait" ] } in
+  let spec = Spec.(stage ~from:"base" [ run "Wait" ]) in
   let r, set_r = Lwt.wait () in
   Mock_sandbox.expect sandbox (mock_op ~result:r ~cancel:set_r ());
   let b = B.build builder context spec in
@@ -251,7 +251,7 @@ let test_cancel _switch () =
 (* Two users are sharing a build. One cancels. *)
 let test_cancel_2 _switch () =
   with_config @@ fun ~src_dir ~store ~sandbox ~builder ->
-  let spec = Spec.{ from = "base"; ops = [ run "Wait" ] } in
+  let spec = Spec.(stage ~from:"base" [ run "Wait" ]) in
   let r, set_r = Lwt.wait () in
   Mock_sandbox.expect sandbox (mock_op ~result:r ~cancel:set_r ~output:(`Constant "ok") ());
   let log1 = Log.create "b1" in
@@ -288,7 +288,7 @@ let test_cancel_2 _switch () =
 (* Two users are sharing a build. Both cancel. *)
 let test_cancel_3 _switch () =
   with_config @@ fun ~src_dir ~store ~sandbox ~builder ->
-  let spec = Spec.{ from = "base"; ops = [ run "Wait" ] } in
+  let spec = Spec.(stage ~from:"base" [ run "Wait" ]) in
   let r, set_r = Lwt.wait () in
   Mock_sandbox.expect sandbox (mock_op ~result:r ~cancel:set_r ());
   let log1 = Log.create "b1" in
@@ -327,7 +327,7 @@ let test_cancel_3 _switch () =
 (* One user cancels a failed build after its replacement has started. *)
 let test_cancel_4 _switch () =
   with_config @@ fun ~src_dir ~store ~sandbox ~builder ->
-  let spec = Spec.{ from = "base"; ops = [ run "Wait" ] } in
+  let spec = Spec.(stage ~from:"base" [ run "Wait" ]) in
   let r, set_r = Lwt.wait () in
   Mock_sandbox.expect sandbox (mock_op ~result:r ~cancel:set_r ());
   let log1 = Log.create "b1" in
@@ -364,7 +364,7 @@ let test_cancel_4 _switch () =
 (* Start a new build while the previous one is cancelling. *)
 let test_cancel_5 _switch () =
   with_config @@ fun ~src_dir ~store ~sandbox ~builder ->
-  let spec = Spec.{ from = "base"; ops = [ run "Wait" ] } in
+  let spec = Spec.(stage ~from:"base" [ run "Wait" ]) in
   let r, set_r = Lwt.wait () in
   let delay_store, set_delay = Lwt.wait () in
   Mock_sandbox.expect sandbox (mock_op ~result:r ~cancel:set_r ~delay_store ());
@@ -390,7 +390,7 @@ let test_cancel_5 _switch () =
 
 let test_delete _switch () =
   with_config @@ fun ~src_dir ~store ~sandbox ~builder ->
-  let spec = Spec.{ from = "base"; ops = [ run "A"; run "B" ] } in
+  let spec = Spec.(stage ~from:"base" [ run "A"; run "B" ]) in
   Mock_sandbox.expect sandbox (mock_op ~output:(`Constant "A") ());
   Mock_sandbox.expect sandbox (mock_op ~output:(`Constant "B") ());
   let log1 = Log.create "b1" in
@@ -438,10 +438,10 @@ let test_sexp () =
   let test name s =
     let s = remove_indent s in
     let s1 = Sexplib.Sexp.of_string s in
-    let stage = Spec.stage_of_sexp s1 in
-    let s2 = Spec.sexp_of_stage stage in
+    let spec = Spec.t_of_sexp s1 in
+    let s2 = Spec.sexp_of_t spec in
     Alcotest.(check sexp) name s1 s2;
-    Alcotest.(check string) name s (Fmt.strf "%a" Spec.pp_stage stage)
+    Alcotest.(check string) name s (Fmt.strf "%a" Spec.pp spec)
   in
   test "copy" {|
      ((from base)
@@ -458,7 +458,7 @@ let test_sexp () =
 
 let test_docker () =
   let test ~buildkit name expect sexp =
-    let spec = Spec.stage_of_sexp (Sexplib.Sexp.of_string sexp) in
+    let spec = Spec.t_of_sexp (Sexplib.Sexp.of_string sexp) in
     let got = Obuilder_spec.Docker.dockerfile_of_spec ~buildkit spec |> Dockerfile.string_of_t in
     let expect = remove_indent expect in
     Alcotest.(check string) name expect got