diff --git a/.ocamlformat b/.ocamlformat
index 07e1516..543ac1b 100644
--- a/.ocamlformat
+++ b/.ocamlformat
@@ -1,3 +1,4 @@
 profile = default
 version = 0.27.0
+ocaml-version = 5.3
 break-sequences = false
diff --git a/acutis.ml b/acutis.ml
index d5ec931..8b29367 100644
--- a/acutis.ml
+++ b/acutis.ml
@@ -154,13 +154,10 @@ end = struct
         type _ Effect.t += Yield : a -> unit Effect.t
       end in
       let yield v = Effect.perform (M.Yield v) in
-      let retc () = Seq.Nil in
-      let effc : type b.
-          b Effect.t -> ((b, _) Effect.Deep.continuation -> _) option = function
-        | M.Yield v -> Some (fun k -> Seq.Cons (v, Effect.Deep.continue k))
-        | _ -> None
-      in
-      fun () -> Effect.Deep.match_with f yield { retc; exnc = raise; effc }
+      fun () ->
+        match f yield with
+        | () -> Seq.Nil
+        | effect M.Yield v, k -> Seq.Cons (v, Effect.Deep.continue k)
 
     let iter s f = Seq.iter f s
     let string_to_seq = String.to_seq
diff --git a/acutis.opam b/acutis.opam
index 08db150..7b1d41b 100644
--- a/acutis.opam
+++ b/acutis.opam
@@ -16,7 +16,7 @@ doc: "https://johnridesa.bike/acutis/"
 bug-reports: "https://github.com/johnridesabike/acutis/issues"
 depends: [
   "dune" {>= "3.13"}
-  "ocaml" {>= "5.2"}
+  "ocaml" {>= "5.3"}
   "menhir"
   "yojson"
   "dune-build-info"
diff --git a/acutis_js.ml b/acutis_js.ml
index f2b82e4..877a200 100644
--- a/acutis_js.ml
+++ b/acutis_js.ml
@@ -110,19 +110,14 @@ module Promise = struct
         Js.Unsafe.inject (Js.wrap_callback reject);
       |]
 
-  module E = Effect
-  module ED = Effect.Deep
+  type _ Effect.t += Await : 'a t -> 'a Effect.t
 
-  type _ E.t += Await : 'a t -> 'a E.t
+  let await p = Effect.perform (Await p)
 
-  let await p = E.perform (Await p)
-
-  let effc : type a. a E.t -> ((a, 'b t) ED.continuation -> 'b t) option =
-    function
-    | Await p -> Some (fun k -> then_ p (ED.continue k) (ED.discontinue k))
-    | _ -> None
-
-  let handle_await f = ED.try_with f () { effc }
+  let handle_await f =
+    match f () with
+    | x -> x
+    | effect Await p, k -> Effect.Deep.(then_ p (continue k) (discontinue k))
 end
 
 let fname_to_compname s =
diff --git a/acutis_js.opam b/acutis_js.opam
index d9a5720..20c3ded 100644
--- a/acutis_js.opam
+++ b/acutis_js.opam
@@ -10,7 +10,7 @@ doc: "https://johnridesa.bike/acutis/"
 bug-reports: "https://github.com/johnridesabike/acutis/issues"
 depends: [
   "dune" {>= "3.13"}
-  "ocaml" {>= "5.0"}
+  "ocaml"
   "acutis" {= version}
   "js_of_ocaml" {>= "5.8.1"}
   "js_of_ocaml-compiler"
diff --git a/dune-project b/dune-project
index 22afc1f..9672bf3 100644
--- a/dune-project
+++ b/dune-project
@@ -29,7 +29,7 @@ compile them to self-contained JavaScript files.
 ")
  (depends
   (ocaml
-   (>= 5.2))
+   (>= 5.3))
   menhir
   yojson
   dune-build-info
@@ -44,8 +44,7 @@ compile them to self-contained JavaScript files.
  (synopsis "A virtual package containing the Acutis JavaScript dependencies")
  (allow_empty)
  (depends
-  (ocaml
-   (>= 5.0))
+  ocaml
   (acutis
    (= :version))
   (js_of_ocaml