diff --git a/pkgs/development/ocaml-modules/gmap/default.nix b/pkgs/development/ocaml-modules/gmap/default.nix
new file mode 100644
index 000000000000..2585dfcaa968
--- /dev/null
+++ b/pkgs/development/ocaml-modules/gmap/default.nix
@@ -0,0 +1,24 @@
+{ lib, buildDunePackage, fetchurl, alcotest }:
+
+buildDunePackage rec {
+  pname = "gmap";
+  version = "0.3.0";
+
+  src = fetchurl {
+    url = "https://github.com/hannesm/gmap/releases/download/${version}/gmap-${version}.tbz";
+    sha256 = "073wa0lrb0jj706j87cwzf1a8d1ff14100mnrjs8z3xc4ri9xp84";
+  };
+
+  minimumOCamlVersion = "4.03";
+
+  buildInputs = [ alcotest ];
+
+  doCheck = true;
+
+  meta = {
+    description = "Heterogenous maps over a GADT";
+    homepage = "https://github.com/hannesm/gmap";
+    license = lib.licenses.isc;
+    maintainers = [ lib.maintainers.vbgl ];
+  };
+}
diff --git a/pkgs/top-level/ocaml-packages.nix b/pkgs/top-level/ocaml-packages.nix
index 72ca022adc64..64e2effa724f 100644
--- a/pkgs/top-level/ocaml-packages.nix
+++ b/pkgs/top-level/ocaml-packages.nix
@@ -273,6 +273,8 @@ let
 
     gen = callPackage ../development/ocaml-modules/gen { };
 
+    gmap = callPackage ../development/ocaml-modules/gmap { };
+
     herelib = callPackage ../development/ocaml-modules/herelib { };
 
     higlo = callPackage ../development/ocaml-modules/higlo { };