diff --git a/pkgs/development/ocaml-modules/hashcons/default.nix b/pkgs/development/ocaml-modules/hashcons/default.nix
new file mode 100644
index 000000000000..2bfaced11551
--- /dev/null
+++ b/pkgs/development/ocaml-modules/hashcons/default.nix
@@ -0,0 +1,23 @@
+{ lib, fetchFromGitHub, buildDunePackage }:
+
+buildDunePackage rec {
+  pname = "hashcons";
+  version = "1.4";
+
+  src = fetchFromGitHub {
+    owner  = "backtracking";
+    repo   = "ocaml-${pname}";
+    rev    = "d733325eeb55878bed285120c2c088daf78f0e2b";
+    sha256 = "0h4pvwj34pndaw3pajkhl710ywwinhc9pqimgllfmkl37wz2d8zq";
+  };
+
+  useDune2 = true;
+
+  doCheck = true;
+
+  meta = {
+    description = "OCaml hash-consing library";
+    license = lib.licenses.lgpl21;
+    maintainers = [ lib.maintainers.ulrikstrid ];
+  };
+}
diff --git a/pkgs/top-level/ocaml-packages.nix b/pkgs/top-level/ocaml-packages.nix
index 91c764cddfd1..f9f2886539fe 100644
--- a/pkgs/top-level/ocaml-packages.nix
+++ b/pkgs/top-level/ocaml-packages.nix
@@ -428,6 +428,8 @@ let
     hacl-star = callPackage ../development/ocaml-modules/hacl-star { };
     hacl-star-raw = callPackage ../development/ocaml-modules/hacl-star/raw.nix { };
 
+    hashcons = callPackage ../development/ocaml-modules/hashcons { };
+
     herelib = callPackage ../development/ocaml-modules/herelib { };
 
     hidapi = callPackage ../development/ocaml-modules/hidapi { };