diff --git a/pkgs/development/ocaml-modules/posix/base.nix b/pkgs/development/ocaml-modules/posix/base.nix
index 7bdf8f0dd5a9..6d0cd879d4e2 100644
--- a/pkgs/development/ocaml-modules/posix/base.nix
+++ b/pkgs/development/ocaml-modules/posix/base.nix
@@ -13,11 +13,10 @@ buildDunePackage rec {
   src = fetchFromGitHub {
     owner = "savonet";
     repo = "ocaml-posix";
-    rev = "v${version}";
+    tag = "v${version}";
     hash = "sha256-JKJIiuo4lW8DmcK1mJlT22784J1NS2ig860jDbRIjIo=";
   };
 
-  duneVersion = "3";
   minimalOCamlVersion = "4.08";
 
   propagatedBuildInputs = [
diff --git a/pkgs/development/ocaml-modules/posix/math2.nix b/pkgs/development/ocaml-modules/posix/math2.nix
new file mode 100644
index 000000000000..e60116f0dedd
--- /dev/null
+++ b/pkgs/development/ocaml-modules/posix/math2.nix
@@ -0,0 +1,19 @@
+{
+  buildDunePackage,
+  posix-base,
+  unix-errno,
+}:
+
+buildDunePackage {
+  pname = "posix-math2";
+  inherit (posix-base) src version;
+
+  propagatedBuildInputs = [
+    posix-base
+    unix-errno
+  ];
+
+  meta = posix-base.meta // {
+    description = "Bindings for posix math";
+  };
+}
diff --git a/pkgs/development/ocaml-modules/posix/socket.nix b/pkgs/development/ocaml-modules/posix/socket.nix
index 4c3c6cc0f02b..47d422b09322 100644
--- a/pkgs/development/ocaml-modules/posix/socket.nix
+++ b/pkgs/development/ocaml-modules/posix/socket.nix
@@ -5,7 +5,7 @@ buildDunePackage {
 
   inherit (posix-base) version src;
 
-  duneVersion = "3";
+  minimalOCamlVersion = "4.12";
 
   propagatedBuildInputs = [ posix-base ];
 
diff --git a/pkgs/development/ocaml-modules/posix/time2.nix b/pkgs/development/ocaml-modules/posix/time2.nix
index a2fc562496b1..158c30e535d8 100644
--- a/pkgs/development/ocaml-modules/posix/time2.nix
+++ b/pkgs/development/ocaml-modules/posix/time2.nix
@@ -11,8 +11,6 @@ buildDunePackage {
 
   inherit (posix-base) version src;
 
-  duneVersion = "3";
-
   propagatedBuildInputs = [
     posix-base
     posix-types
diff --git a/pkgs/development/ocaml-modules/posix/types.nix b/pkgs/development/ocaml-modules/posix/types.nix
index 8672a7dc29f8..db8529464411 100644
--- a/pkgs/development/ocaml-modules/posix/types.nix
+++ b/pkgs/development/ocaml-modules/posix/types.nix
@@ -5,9 +5,6 @@ buildDunePackage {
 
   inherit (posix-base) version src;
 
-  minimalOCamlVersion = "4.03";
-  duneVersion = "3";
-
   propagatedBuildInputs = [ posix-base ];
 
   meta = posix-base.meta // {
diff --git a/pkgs/top-level/ocaml-packages.nix b/pkgs/top-level/ocaml-packages.nix
index d2dae1c3e383..126211f525a5 100644
--- a/pkgs/top-level/ocaml-packages.nix
+++ b/pkgs/top-level/ocaml-packages.nix
@@ -1570,6 +1570,8 @@ let
 
     posix-base = callPackage ../development/ocaml-modules/posix/base.nix { };
 
+    posix-math2 = callPackage ../development/ocaml-modules/posix/math2.nix { };
+
     posix-socket = callPackage ../development/ocaml-modules/posix/socket.nix { };
 
     posix-time2 = callPackage ../development/ocaml-modules/posix/time2.nix { };