diff --git a/pkgs/development/ocaml-modules/dyn/default.nix b/pkgs/development/ocaml-modules/dyn/default.nix
new file mode 100644
index 000000000000..81b9e0d745fb
--- /dev/null
+++ b/pkgs/development/ocaml-modules/dyn/default.nix
@@ -0,0 +1,16 @@
+{ lib, buildDunePackage, dune_3, ordering }:
+
+buildDunePackage {
+  pname = "dyn";
+  inherit (dune_3) version src;
+  duneVersion = "3";
+
+  dontAddPrefix = true;
+
+  propagatedBuildInputs = [ ordering ];
+
+  meta = dune_3.meta // {
+    description = "Dynamic type";
+  };
+}
+
diff --git a/pkgs/top-level/ocaml-packages.nix b/pkgs/top-level/ocaml-packages.nix
index f733e01aedda..c7f2d04bbee0 100644
--- a/pkgs/top-level/ocaml-packages.nix
+++ b/pkgs/top-level/ocaml-packages.nix
@@ -330,6 +330,8 @@ let
 
     duration =  callPackage ../development/ocaml-modules/duration { };
 
+    dyn =  callPackage ../development/ocaml-modules/dyn { };
+
     earley = callPackage ../development/ocaml-modules/earley { };
 
     earlybird = callPackage ../development/ocaml-modules/earlybird { };