diff --git a/pkgs/cheriot-sim.nix b/pkgs/cheriot-sim.nix
index 05fcd50..3fb5d57 100644
--- a/pkgs/cheriot-sim.nix
+++ b/pkgs/cheriot-sim.nix
@@ -13,53 +13,64 @@
   pkg-config,
   gnumake,
   z3,
-}:
-stdenv.mkDerivation rec {
-  pname = "cheriot-sim";
-  version = "e5038a0";
+  darwin,
+}: let
+  sail = ocamlPackages.sail.overrideAttrs (prev: {
+    # On MacOS sail needs to access the codesign package.
+    nativeBuildInputs = prev.nativeBuildInputs ++ lib.optional stdenv.isDarwin darwin.sigtool;
+  });
+in
+  stdenv.mkDerivation rec {
+    pname = "cheriot-sim";
+    version = "e5038a0";
 
-  src = fetchFromGitHub {
-    owner = "microsoft";
-    repo = "cheriot-sail";
-    rev = "e5038a0ec5fcdf2f672d0a7ddf8446225fd86cf7";
-    fetchSubmodules = true;
-    hash = "sha256-umMN2ktOeV2Queocgi8qlYO464v/98+uTgbCkO9yLBA=";
-  };
+    src = fetchFromGitHub {
+      owner = "microsoft";
+      repo = "cheriot-sail";
+      rev = "e5038a0ec5fcdf2f672d0a7ddf8446225fd86cf7";
+      fetchSubmodules = true;
+      hash = "sha256-umMN2ktOeV2Queocgi8qlYO464v/98+uTgbCkO9yLBA=";
+    };
 
-  buildInputs = [
-    zlib
-    gmp
-  ];
+    buildInputs = [
+      zlib
+      gmp
+    ];
 
-  nativeBuildInputs = [
-    ocaml
-    pkg-config
-    gnumake
-    z3
-  ];
+    nativeBuildInputs = [
+      ocaml
+      pkg-config
+      gnumake
+      z3
+    ];
 
-  postPatch = ''
-    for file in riscv_patches/*.patch; do
-      (cd sail-riscv; patch -p1 < "../$file")
-    done
-  '';
+    postPatch =
+      ''
+        for file in riscv_patches/*.patch; do
+          (cd sail-riscv; patch -p1 < "../$file")
+        done
+      ''
+      + lib.optionalString stdenv.isDarwin ''
+        # If LTO is enabled, LLVM bitcode is produced and linking produces unrecognized file error.
+        substituteInPlace Makefile --replace " -flto" ""
+      '';
 
-  makeFlags = [
-    "SAIL=${ocamlPackages.sail}/bin/sail"
-    "SAIL_DIR=${ocamlPackages.sail}/share/sail"
-    "LEM_DIR=${ocamlPackages.lem}/share/lem"
-    "csim"
-  ];
+    makeFlags = [
+      "SAIL=${sail}/bin/sail"
+      "SAIL_DIR=${sail}/share/sail"
+      "LEM_DIR=${ocamlPackages.lem}/share/lem"
+      "csim"
+    ];
 
-  installPhase = ''
-    mkdir -p $out/bin
-    cp c_emulator/cheriot_sim $out/bin/
-  '';
+    installPhase = ''
+      mkdir -p $out/bin
+      cp c_emulator/cheriot_sim $out/bin/
+    '';
 
-  meta = {
-    description = "Simulator built from the sail code model of the CHERIoT ISA";
-    homepage = "https://github.com/microsoft/cheriot-sail";
-    license = lib.licenses.bsd2;
-    mainProgram = "cheriot_sim";
-  };
-}
+    meta = {
+      description = "Simulator built from the sail code model of the CHERIoT ISA";
+      homepage = "https://github.com/microsoft/cheriot-sail";
+      license = lib.licenses.bsd2;
+      mainProgram = "cheriot_sim";
+    };
+  }
diff --git a/pkgs/python_ot/default.nix b/pkgs/python_ot/default.nix
index 7b2073a..7c7fd14 100644
--- a/pkgs/python_ot/default.nix
+++ b/pkgs/python_ot/default.nix
@@ -5,6 +5,7 @@
   inputs,
   pkgs,
   python3,
+  lib,
   ...
 }: let
   # This overlay is generated by poetry2nix
@@ -12,12 +13,21 @@
 
   poetry2nix = inputs.poetry2nix.lib.mkPoetry2Nix {inherit pkgs;};
   poetryOverrides = inputs.self.lib.poetryOverrides {inherit pkgs;};
-in
-  poetry2nix.mkPoetryEnv {
+
+  env = poetry2nix.mkPoetryEnv {
     projectDir = ./.;
     overrides = [
       poetry-git-overlay
       poetryOverrides
       poetry2nix.defaultPoetryOverrides
     ];
+  };
+in
+  env
+  // {
+    meta =
+      env.meta
+      // {
+        platforms = lib.platforms.linux;
+      };
   }