diff --git a/nix/onixPackages/default.nix b/nix/onixPackages/default.nix
index 67781f1..13c68a8 100644
--- a/nix/onixPackages/default.nix
+++ b/nix/onixPackages/default.nix
@@ -7,5 +7,22 @@ ocamlPackages.overrideScope (self: super: {
   yojson = super.yojson.overrideAttrs (_: { doCheck = false; });
   uri = super.uri.overrideAttrs (_: { doCheck = false; });
   angstrom = super.angstrom.overrideAttrs (_: { doCheck = false; });
+  opam-repository = super.opam-repository.overrideAttrs (_: {
+    configureFlags = [
+      "--disable-checks"
+    ];
+    doCheck = false;
+  });
   logs = super.logs.override { jsooSupport = false; };
+  opam-core = super.opam-core.overrideAttrs (attrs: {
+    propagatedBuildInputs = attrs.propagatedBuildInputs ++ [
+      ocamlPackages.uutf
+      ocamlPackages.jsonm
+      ocamlPackages.sha
+      self.swhid_core
+      self.spdx_licenses
+    ];
+  });
+  swhid_core = self.callPackage ./swhid_core.nix {};
+  spdx_licenses = self.callPackage ./spdx_licenses.nix {};
 })
diff --git a/nix/onixPackages/spdx_licenses.nix b/nix/onixPackages/spdx_licenses.nix
new file mode 100644
index 0000000..dc1dd08
--- /dev/null
+++ b/nix/onixPackages/spdx_licenses.nix
@@ -0,0 +1,20 @@
+{ lib, fetchurl, buildDunePackage }:
+
+buildDunePackage rec {
+  pname = "spdx_licenses";
+  version = "1.2.0";
+  useDune2 = true;
+
+  src = fetchurl {
+    url =
+      "https://github.com/kit-ty-kate/spdx_licenses/releases/download/v1.2.0/spdx_licenses-1.2.0.tar.gz";
+    sha256 = "sha256-9ViB7PRDz70w3RJczapgn2tJx9wTWgAbdzos6r3J2r4=";
+  };
+
+  meta = with lib; {
+    description = "spdx_licenses";
+    homepage = "https://github.com/kit-ty-kate/spdx_licenses";
+    license = licenses.mit;
+    maintainers = [ ];
+  };
+}
diff --git a/nix/onixPackages/swhid_core.nix b/nix/onixPackages/swhid_core.nix
new file mode 100644
index 0000000..678eb60
--- /dev/null
+++ b/nix/onixPackages/swhid_core.nix
@@ -0,0 +1,20 @@
+{ lib, fetchurl, buildDunePackage }:
+
+buildDunePackage rec {
+  pname = "swhid_core";
+  version = "0.1";
+  useDune2 = true;
+
+  src = fetchurl {
+    url =
+      "https://github.com/OCamlPro/swhid_core/archive/refs/tags/0.1.tar.gz";
+    sha256 = "sha256-hxi065fJ8KzW2RYqnvovavgkdKC9GG9iL9oylPdzvM8=";
+  };
+
+  meta = with lib; {
+    description = "swhid_core";
+    homepage = "https://github.com/OCamlPro/swhid_core";
+    license = licenses.isc;
+    maintainers = [ ];
+  };
+}
diff --git a/src/onix_core/System.ml b/src/onix_core/System.ml
index 1dc6174..e0c11f9 100644
--- a/src/onix_core/System.ml
+++ b/src/onix_core/System.ml
@@ -13,8 +13,8 @@ let os_list = ["linux"; "macos"]
 let arch_list = ["x86_64"; "arm64"]
 
 let host =
-  let arch = OpamSysPoll.arch () in
-  let os = OpamSysPoll.os () in
+  let arch = OpamSysPoll.arch OpamVariable.Map.empty in
+  let os = OpamSysPoll.os OpamVariable.Map.empty in
   match (arch, os) with
   | Some arch, Some os -> { arch; os }
   | Some _, None -> failwith "could not get host's 'os'"