diff --git a/pkgs/applications/science/logic/mcy/default.nix b/pkgs/applications/science/logic/mcy/default.nix
new file mode 100644
index 000000000000..9f239f221b18
--- /dev/null
+++ b/pkgs/applications/science/logic/mcy/default.nix
@@ -0,0 +1,41 @@
+{ stdenv, fetchFromGitHub
+, yosys, symbiyosys, python3
+}:
+
+let
+  python = python3.withPackages (p: with p; [ flask ]);
+in
+stdenv.mkDerivation {
+  pname = "mcy";
+  version = "2020.02.05";
+
+  src = fetchFromGitHub {
+    owner  = "YosysHQ";
+    repo   = "mcy";
+    rev    = "83deeddd12d583a89ad4aa1d2147efa4d6adc33c";
+    sha256 = "1i0cabiqr68zflwzc6z894i4n7k6m3hbfck58vzh8zb9jwxwizav";
+  };
+
+  buildInputs = [ python ];
+  patchPhase = ''
+    substituteInPlace mcy.py \
+      --replace yosys '${yosys}/bin/yosys' \
+      --replace 'os.execvp("mcy-dash"' "os.execvp(\"$out/libexec/mcy/mcy-dash.py\""
+  '';
+
+  # the build needs a bit of work...
+  buildPhase = "true";
+  installPhase = ''
+    mkdir -p $out/bin $out/libexec/mcy
+    install mcy.py $out/bin/mcy && chmod +x $out/bin/mcy
+    install mcy-dash.py $out/libexec/mcy/mcy-dash.py
+  '';
+
+  meta = {
+    description = "Mutation-based coverage testing for hardware designs, with Yosys";
+    homepage    = "https://github.com/YosysHQ/mcy";
+    license     = stdenv.lib.licenses.isc;
+    maintainers = with stdenv.lib.maintainers; [ thoughtpolice ];
+    platforms   = stdenv.lib.platforms.all;
+  };
+}
diff --git a/pkgs/top-level/all-packages.nix b/pkgs/top-level/all-packages.nix
index 0679f2ddd73b..3004e0fac1ee 100644
--- a/pkgs/top-level/all-packages.nix
+++ b/pkgs/top-level/all-packages.nix
@@ -24503,6 +24503,8 @@ in
 
   symbiyosys = callPackage ../applications/science/logic/symbiyosys {};
 
+  mcy = callPackage ../applications/science/logic/mcy {};
+
   lingeling = callPackage ../applications/science/logic/lingeling {};
 
   ### SCIENCE / ELECTRONICS