diff --git a/pkgs/development/ocaml-modules/eliom/default.nix b/pkgs/development/ocaml-modules/eliom/default.nix
index b8d90d0d2b7..92d89afe398 100644
--- a/pkgs/development/ocaml-modules/eliom/default.nix
+++ b/pkgs/development/ocaml-modules/eliom/default.nix
@@ -1,4 +1,4 @@
-{ stdenv, lib, fetchzip, which, ocsigen_server, ocaml,
+{ stdenv, lib, fetchzip, fetchpatch, which, ocsigen_server, ocaml,
   lwt_react,
   opaline, ppx_deriving, findlib
 , ocaml-migrate-parsetree
@@ -23,6 +23,14 @@ stdenv.mkDerivation rec
     sha256 = "00m6v2k4mg8705dy41934lznl6gj91i6dk7p1nkaccm51nna25kz";
   };
 
+  patches = [
+    # Compatibility with js_of_ocaml >= 3.9.0, remove at next release
+    (fetchpatch {
+      url = "https://github.com/ocsigen/eliom/commit/4106a4217956f7b74a8ef3f73a1e1f55e02ade45.patch";
+      sha256 = "1cgbvpljn9x6zxirxf3rdjrsdwy319ykz3qq03c36cc40hy2w13p";
+    })
+  ];
+
   buildInputs = [ ocaml which findlib js_of_ocaml-ocamlbuild
     ocaml-migrate-parsetree
     js_of_ocaml-ppx_deriving_json opaline
diff --git a/pkgs/development/tools/ocaml/js_of_ocaml/compiler.nix b/pkgs/development/tools/ocaml/js_of_ocaml/compiler.nix
index f1398c2f7c7..12306d2a305 100644
--- a/pkgs/development/tools/ocaml/js_of_ocaml/compiler.nix
+++ b/pkgs/development/tools/ocaml/js_of_ocaml/compiler.nix
@@ -1,16 +1,16 @@
 { lib, fetchurl, buildDunePackage
-, cmdliner, cppo, yojson, ppxlib
+, ocaml, cmdliner, cppo, yojson, ppxlib
 , menhir
 }:
 
 buildDunePackage rec {
   pname = "js_of_ocaml-compiler";
-  version = "3.8.0";
+  version = "3.9.1";
   useDune2 = true;
 
   src = fetchurl {
     url = "https://github.com/ocsigen/js_of_ocaml/releases/download/${version}/js_of_ocaml-${version}.tbz";
-    sha256 = "069jyiayxcgwnips3adxb3d53mzd4rrq2783b9fgmsiyzm545lcy";
+    sha256 = "0ib551kfsjlp9vr3fk36hrbq7xxyl8bj6vcn3ccr0s370bsmgpm6";
   };
 
   nativeBuildInputs = [ cppo menhir ];