diff --git a/default.nix b/default.nix
index 9b470bb..f279e0f 100644
--- a/default.nix
+++ b/default.nix
@@ -16,6 +16,11 @@ final: prev: {
 
     crystal = prev.callPackage ./pokecrystal { };
 
+    ruby = prev.callPackage ./pokeruby { };
+    ruby-modern = prev.callPackage ./pokeruby { modern = true; };
+    ruby-de = prev.callPackage ./pokeruby { german = true; }; # german version
+    ruby-de-modern = prev.callPackage ./pokeruby { german = true; modern = true; };
+
     all = prev.callPackage ./pokeall { };
   };
 }
diff --git a/pokeruby/default.nix b/pokeruby/default.nix
new file mode 100644
index 0000000..c17e175
--- /dev/null
+++ b/pokeruby/default.nix
@@ -0,0 +1,53 @@
+{ lib, stdenv, fetchFromGitHub, libpng, agbcc, gcc-arm-embedded, rsync, modern ? false, roms ? null, german ? false }:
+let
+  roms' =
+    if roms == null
+    then
+      (if german
+      then [ "ruby_de" "ruby_de_rev1" "sapphire_de" "sapphire_de_rev1" ]
+      else [ "ruby" "ruby_rev1" "ruby_rev2" "sapphire" "sapphire_rev1" "sapphire_rev2" ])
+    else roms;
+in
+stdenv.mkDerivation rec {
+  pname = "pokeruby${lib.optionalString german "-de"}${lib.optionalString modern "-modern"}";
+  version = "unstable-2021-07-16";
+
+  src = fetchFromGitHub {
+    owner = "pret";
+    repo = "pokeruby";
+    rev = "7cc7f95aa646bb38cb4c29e4422df7b6f1ffd81e";
+    sha256 = "sha256-i4MOcvJQTAoWJRgf0l0oSSFz2MoUzD4+ADmvhldytg4=";
+  };
+
+  nativeBuildInputs = [ gcc-arm-embedded ] ++ lib.optional german rsync;
+  buildInputs = [ libpng ];
+
+  postPatch = ''
+    ln -s ${agbcc}/tools/agbcc tools/
+  '';
+
+  preBuild = lib.optionalString german ''
+    bash de_before.sh
+  '';
+
+  makeFlags = [
+    "TOOLCHAIN=${gcc-arm-embedded}"
+    "MODERN=${if modern then "1" else "0"}"
+  ] ++ roms';
+
+  enableParallelBuilding = true;
+
+  installPhase = ''
+    runHook preInstall
+    mkdir -p $out
+    cp poke{${lib.concatStringsSep "," roms'}}${lib.optionalString modern "_modern"}.gba $out
+    runHook postInstall
+  '';
+
+  meta = with lib; {
+    description = "ROM built from disassembly of Pokémon Ruby/Sapphire";
+    homepage = "https://github.com/pret/pokeruby";
+    license = licenses.unfree;
+    maintainers = with maintainers; [ sbruder ];
+  };
+}