diff --git a/flake.nix b/flake.nix
index 46bb072..fddface 100644
--- a/flake.nix
+++ b/flake.nix
@@ -1,4 +1,5 @@
 {
+# vim: set et,sw=4
   description = "Flake utils demo";
 
   inputs.flake-utils.url = "github:numtide/flake-utils";
@@ -9,6 +10,40 @@
       {
         packages = rec {
           performous-composer = pkgs.libsForQt5.callPackage ./performous-composer.nix {};
+          open-simh = pkgs.stdenv.mkDerivation {
+            pname = "open-simh";
+            version = "4.0.0";
+            src = pkgs.fetchFromGitHub {
+              owner = "open-simh";
+              repo = "simh";
+              rev = "d4f85d01bdf7301d5f7a2c4e51c3a84024561b26";
+              sha256 = "sha256-kjLX8JeG7nPNz7KLheQCKz8kKA1xPn0CpRg+N336r1w=";
+            };
+            postPatch = ''
+              ${pkgs.ed}/bin/ed BESM6/CMakeLists.txt <<'_EOF_'
+              /foreach (fdir \''${cand_fontdirs})/
+              i
+              string(REPLACE " " ";" extra_cand_fontdirs "$ENV{buildInputs} $ENV{nativeBuildInputs}")
+              foreach(extra_fdir IN LISTS extra_cand_fontdirs)
+                  list(APPEND cand_fontdirs ''${extra_fdir})
+              endforeach()
+              .
+              wq
+              _EOF_'';
+            buildInputs = with pkgs; [
+              libpcap
+              vde2
+              pcre
+              libedit
+              SDL2 SDL2_ttf
+              libpng
+              zlib
+              freetype
+              pkg-config
+              dejavu_fonts
+            ];
+            nativeBuildInputs = [ pkgs.cmake pkgs.ninja ];
+          };
         };
         apps = rec {
           hello = flake-utils.lib.mkApp { drv = self.packages.${system}.hello; };