diff --git a/CMakeLists.txt b/CMakeLists.txt
index 63947175..6e4cc001 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -92,6 +92,8 @@ add_subdirectory(xo-pywebsock)
 add_subdirectory(xo-statistics)
 add_subdirectory(xo-distribution)
 add_subdirectory(xo-pydistribution)
+add_subdirectory(xo-simulator)
+#add_subdirectory(xo-process)
 #
 add_subdirectory(xo-expression)
 add_subdirectory(xo-pyexpression)
@@ -100,7 +102,6 @@ add_subdirectory(xo-reader)
 add_subdirectory(xo-jit)
 add_subdirectory(xo-pyjit)
 #
-#add_subdirectory(xo-simulator)
 #add_subdirectory(xo-pysimulator)
 #add_subdirectory(xo-process)
 #add_subdirectory(xo-pyprocess)
diff --git a/default.nix b/default.nix
index d25b6e70..a255e23b 100644
--- a/default.nix
+++ b/default.nix
@@ -65,6 +65,8 @@ let
           xo-statistics     = self.callPackage pkgs/xo-statistics.nix     {};
           xo-distribution   = self.callPackage pkgs/xo-distribution.nix   {};
           xo-pydistribution = self.callPackage pkgs/xo-pydistribution.nix {};
+          xo-simulator      = self.callPackage pkgs/xo-simulator.nix      {};
+#          xo-process        = self.callPackage pkgs/xo-process.nix        {};
 #
           xo-expression     = self.callPackage pkgs/xo-expression.nix     {};
           xo-pyexpression   = self.callPackage pkgs/xo-pyexpression.nix   {};
@@ -76,9 +78,7 @@ let
                                                                             llvm = llvmPackages.llvm; };
           xo-pyjit          = self.callPackage pkgs/xo-pyjit.nix          {};
 
-#          xo-simulator      = self.callPackage pkgs/xo-simulator.nix      {};
 #          xo-pysimulator    = self.callPackage pkgs/xo-pysimulator.nix    {};
-#          xo-process        = self.callPackage pkgs/xo-process.nix        {};
 #          xo-pyprocess      = self.callPackage pkgs/xo-pyprocess.nix      {};
 #          xo-kalmanfilter   = self.callPackage pkgs/xo-kalmanfilter.nix   {};
 #          xo-pykalmanfilter = self.callPackage pkgs/xo-pykalmanfilter.nix {};
diff --git a/pkgs/xo-simulator.nix b/pkgs/xo-simulator.nix
new file mode 100644
index 00000000..90ebcdfb
--- /dev/null
+++ b/pkgs/xo-simulator.nix
@@ -0,0 +1,30 @@
+{
+  # nixpkgs dependencies
+  stdenv, cmake, catch2,
+
+  # xo dependencies
+  xo-cmake,
+#  xo-refcnt,
+#  xo-reflect,
+  xo-reactor,
+    #, xo-indentlog,
+} :
+
+stdenv.mkDerivation (finalattrs:
+  {
+    name = "xo-simulator";
+
+    src = ../xo-simulator;
+
+    cmakeFlags = ["-DCMAKE_MODULE_PATH=${xo-cmake}/share/cmake"];
+    doCheck = true;
+    nativeBuildInputs = [
+      cmake catch2 xo-cmake
+    ];
+    propagatedBuildInputs = [
+      xo-reactor
+#      xo-refcnt
+#      xo-reflect
+#      xo-indentlog
+    ];
+  })
diff --git a/pkgs/xo-userenv.nix b/pkgs/xo-userenv.nix
index c1d1c02c..aba839a4 100644
--- a/pkgs/xo-userenv.nix
+++ b/pkgs/xo-userenv.nix
@@ -50,9 +50,10 @@
   xo-statistics,
   xo-distribution,
   xo-pydistribution,
-#  xo-simulator,
+  xo-simulator,
+#  xo-process,
   #  xo-pysimulator,
-  #xo-process, xo-pyprocess,
+  #xo-pyprocess,
   #xo-kalmanfilter,
   #  xo-pykalmanfilter,
 #
@@ -97,6 +98,8 @@ buildEnv {
             xo-statistics
             xo-distribution
             xo-pydistribution
+            xo-simulator
+#            xo-process
 #
             xo-expression
             xo-pyexpression
@@ -104,9 +107,7 @@ buildEnv {
             xo-reader
             xo-jit
             xo-pyjit
-#            xo-simulator
 #            xo-pysimulator
-#            xo-process
 #            xo-pyprocess
 #            xo-kalmanfilter
 #            xo-pykalmanfilter