diff --git a/.ocamlformat b/.ocamlformat
index c870de9..e80baea 100644
--- a/.ocamlformat
+++ b/.ocamlformat
@@ -1 +1 @@
-version=0.26.1
+version=0.27.0
diff --git a/dune-project b/dune-project
index 1a86c4b..48d12cf 100644
--- a/dune-project
+++ b/dune-project
@@ -26,6 +26,6 @@
  (description "An Eio counterpart to package js_of_ocaml-lwt.")
  (depends
   (eio_js_backend (= :version))
-  (js_of_ocaml-ppx (>= "5.0.1"))
-  (js_of_ocaml (>= 5.0.1))))
+  (js_of_ocaml-ppx (>= "6.0.0"))
+  (js_of_ocaml (>= 6.0.0))))
 (using mdx 0.2)
diff --git a/js_of_ocaml-eio.opam b/js_of_ocaml-eio.opam
index 219fd96..621c896 100644
--- a/js_of_ocaml-eio.opam
+++ b/js_of_ocaml-eio.opam
@@ -11,8 +11,8 @@ bug-reports: "https://github.com/ocaml-multicore/eio_js/issues"
 depends: [
   "dune" {>= "3.9"}
   "eio_js_backend" {= version}
-  "js_of_ocaml-ppx" {>= "5.0.1"}
-  "js_of_ocaml" {>= "5.0.1"}
+  "js_of_ocaml-ppx" {>= "6.0.0"}
+  "js_of_ocaml" {>= "6.0.0"}
   "odoc" {with-doc}
 ]
 build: [
diff --git a/lib_eio_js_backend/eio_js_backend.ml b/lib_eio_js_backend/eio_js_backend.ml
index 32f0b76..358bbcb 100644
--- a/lib_eio_js_backend/eio_js_backend.ml
+++ b/lib_eio_js_backend/eio_js_backend.ml
@@ -133,8 +133,11 @@ let start main =
             !uncaught_exception_handler ex bt;
             Scheduler.next ());
         effc =
-          (fun (type a) (e : a Effect.t) :
-               ((a, suspend) Effect.Deep.continuation -> suspend) option ->
+          (fun (type a)
+            (e : a Effect.t)
+            :
+            ((a, suspend) Effect.Deep.continuation -> suspend) option
+          ->
             match e with
             | Eio.Private.Effects.Suspend f ->
                 Some
diff --git a/lib_js_of_ocaml_eio/examples/boulderdash/boulderdash.ml b/lib_js_of_ocaml_eio/examples/boulderdash/boulderdash.ml
index 1eadc1c..065b95b 100644
--- a/lib_js_of_ocaml_eio/examples/boulderdash/boulderdash.ml
+++ b/lib_js_of_ocaml_eio/examples/boulderdash/boulderdash.ml
@@ -421,11 +421,11 @@ let start _ =
         let t0 = Sys.time () in
         let rec fade () =
           let t = Sys.time () in
-          if t -. t0 >= 1. then table##.style##.opacity := Js.def (js "1")
+          if t -. t0 >= 1. then table##.style##.opacity := js "1"
           else (
             Eio_js.sleep 0.05;
             table##.style##.opacity
-            := Js.def (js (Printf.sprintf "%g" (t -. t0)));
+            := js (Printf.sprintf "%g" (t -. t0));
             fade ())
         in
         fade ();
diff --git a/lib_js_of_ocaml_eio/js_events.ml b/lib_js_of_ocaml_eio/js_events.ml
index 7f3e112..c5cd4b2 100644
--- a/lib_js_of_ocaml_eio/js_events.ml
+++ b/lib_js_of_ocaml_eio/js_events.ml
@@ -50,7 +50,7 @@ let make_event event_kind ?use_capture ?passive target =
 type cancel = { cancel : unit -> unit }
 
 let with_error_log f x =
-  try f x with e -> Firebug.console##log (Js.string (Printexc.to_string e))
+  try f x with e -> Console.console##log (Js.string (Printexc.to_string e))
 
 let seq_loop ~sw evh ?(cancel_handler = false) ?use_capture ?passive target
     handler =
@@ -327,11 +327,11 @@ let mousewheel ?use_capture ?passive target =
              ?capture:(opt_map Js.bool use_capture)
              ?passive:(opt_map Js.bool passive) target
              (fun (ev : #Dom_html.event Js.t) ~dx ~dy ->
-               Firebug.console##log ev;
+               Console.console##log ev;
                cancel ();
                resolve (ev, (dx, dy));
                Js.bool true)
-             (* true because we do not want to prevent default ->
+          (* true because we do not want to prevent default ->
                                the user can use the preventDefault function
                                above. *));
       cancel)
@@ -605,7 +605,7 @@ let request_animation_frame () =
   Eio_js_backend.await
     ~setup:(fun ~resolve ~reject:_ ->
       Dom_html.window##requestAnimationFrame
-        (Js.wrap_callback (fun (_ : float) -> resolve ())))
+        (Js.wrap_callback (fun _ -> resolve ())))
     ~cancel:(fun id -> Dom_html.window##cancelAnimationFrame id)
 
 let onload () = make_event Dom_html.Event.load Dom_html.window
diff --git a/lib_js_of_ocaml_eio/xmlHttpRequest.ml b/lib_js_of_ocaml_eio/xmlHttpRequest.ml
index 79cca21..57aa074 100644
--- a/lib_js_of_ocaml_eio/xmlHttpRequest.ml
+++ b/lib_js_of_ocaml_eio/xmlHttpRequest.ml
@@ -222,9 +222,7 @@ let perform_raw ?(headers = []) ?content_type ?(get_args = [])
             (* IE doesn't have the same semantics for HEADERS_RECEIVED.
                  so we wait til LOADING to check headers. See:
                  http://msdn.microsoft.com/en-us/library/ms534361(v=vs.85).aspx *)
-            | HEADERS_RECEIVED when not Dom_html.onIE ->
-                ignore (do_check_headers ())
-            | LOADING when Dom_html.onIE -> ignore (do_check_headers ())
+            | HEADERS_RECEIVED -> ignore (do_check_headers ())
             | DONE ->
                 (* If we didn't catch a previous event, we check the header. *)
                 if do_check_headers () then
@@ -247,14 +245,13 @@ let perform_raw ?(headers = []) ?content_type ?(get_args = [])
                 progress e##.loaded e##.total;
                 Js._true)
       | None -> ());
-      Optdef.iter req##.upload (fun upload ->
-          match upload_progress with
-          | Some upload_progress ->
-              upload##.onprogress :=
-                Dom.handler (fun e ->
-                    upload_progress e##.loaded e##.total;
-                    Js._true)
-          | None -> ());
+      (match upload_progress with
+      | Some upload_progress ->
+          req##.upload##.onprogress
+          := Dom.handler (fun e ->
+                 upload_progress e##.loaded e##.total;
+                 Js._true)
+      | None -> ());
       (match contents with
       | None -> req##send Js.null
       | Some (`Form_contents (`Fields l)) ->