diff --git a/pkgs/development/ocaml-modules/extunix/default.nix b/pkgs/development/ocaml-modules/extunix/default.nix
new file mode 100644
index 000000000000..da2bc782a2a1
--- /dev/null
+++ b/pkgs/development/ocaml-modules/extunix/default.nix
@@ -0,0 +1,42 @@
+{
+  lib,
+  buildDunePackage,
+  fetchFromGitHub,
+  dune-configurator,
+  ppxlib,
+}:
+
+buildDunePackage (finalAttrs: {
+  pname = "extunix";
+  version = "0.4.4";
+
+  src = fetchFromGitHub {
+    owner = "ygrek";
+    repo = "extunix";
+    tag = "v${finalAttrs.version}";
+    hash = "sha256-7wJDGv19etkDHRwwQ+WONtJswxNMjr2Q2Vhis4WgFek=";
+  };
+
+  postPatch = ''
+    substituteInPlace src/dune --replace-fail 'libraries unix bigarray bytes' 'libraries unix bigarray'
+  '';
+
+  buildInputs = [
+    dune-configurator
+  ];
+
+  propagatedBuildInputs = [
+    ppxlib
+  ];
+
+  # need absolute paths outside from sandbox
+  doCheck = false;
+
+  meta = {
+    description = "Collection of thin bindings to various low-level system API";
+    homepage = "https://github.com/ygrek/extunix";
+    changelog = "https://github.com/ygrek/extunix/releases/tag/v${finalAttrs.version}";
+    license = lib.licenses.lgpl21Only;
+    maintainers = with lib.maintainers; [ redianthus ];
+  };
+})
diff --git a/pkgs/top-level/ocaml-packages.nix b/pkgs/top-level/ocaml-packages.nix
index f109780364a2..c562d1c57f01 100644
--- a/pkgs/top-level/ocaml-packages.nix
+++ b/pkgs/top-level/ocaml-packages.nix
@@ -574,6 +574,8 @@ let
 
         extlib-1-7-7 = callPackage ../development/ocaml-modules/extlib/1.7.7.nix { };
 
+        extunix = callPackage ../development/ocaml-modules/extunix/default.nix { };
+
         ezjsonm = callPackage ../development/ocaml-modules/ezjsonm { };
 
         ezjsonm-encoding = callPackage ../development/ocaml-modules/ezjsonm-encoding { };