diff --git a/rggen_backdoor.sv b/rggen_backdoor.sv
index 87d8b00..cae70c1 100644
--- a/rggen_backdoor.sv
+++ b/rggen_backdoor.sv
@@ -1,7 +1,6 @@
 `ifdef RGGEN_ENABLE_BACKDOOR
 module rggen_backdoor #(
-  parameter int DATA_WIDTH          = 32,
-  parameter bit INSIDE_VHDL_DESIGN  = 0
+  parameter int DATA_WIDTH  = 32
 )(
   input   logic                   i_clk,
   input   logic                   i_rst_n,
@@ -39,7 +38,7 @@ module rggen_backdoor #(
   end
 
   initial begin
-    rggen_backdoor_pkg::set_backdoor_vif($sformatf("%m"), INSIDE_VHDL_DESIGN, backdoor_if);
+    rggen_backdoor_pkg::set_backdoor_vif($sformatf("%m"), backdoor_if);
   end
 endmodule
 `endif
diff --git a/rggen_backdoor_pkg.sv b/rggen_backdoor_pkg.sv
index 6c882c4..dce0576 100644
--- a/rggen_backdoor_pkg.sv
+++ b/rggen_backdoor_pkg.sv
@@ -4,43 +4,73 @@
 `ifdef RGGEN_ENABLE_BACKDOOR
 package rggen_backdoor_pkg;
   typedef virtual rggen_backdoor_if rggen_backdoor_vif;
-  rggen_backdoor_vif  backdoor_vif[string];
 
-  function automatic void set_backdoor_vif(
-    string              hdl_path,
-    bit                 inside_vhdl_design,
-    rggen_backdoor_vif  vif
-  );
-    string  path;
+  class rggen_backdoor_if_store;
+`ifndef XILINX_SIMULATOR
+    protected rggen_backdoor_vif  vif[string];
 
-    if (inside_vhdl_design) begin
-      path  = normalize_hdl_path(hdl_path);
-    end
-    else begin
-      path  = hdl_path;
-    end
+    function void set(string hdl_path, rggen_backdoor_vif vif);
+      string  path;
+      path            = normalize_hdl_path(hdl_path);
+      this.vif[path]  = vif;
+    endfunction
 
-    backdoor_vif[path]  = vif;
-  endfunction
+    function rggen_backdoor_vif get(string hdl_path);
+      return vif[hdl_path];
+    endfunction
+`else
+    class rggen_backdoor_if_wrapper;
+      rggen_backdoor_vif  vif;
+      function new(rggen_backdoor_vif vif);
+        this.vif  = vif;
+      endfunction
+    endclass
+
+    protected rggen_backdoor_if_wrapper vif_wrapper[string];
 
-  function automatic string normalize_hdl_path(
-    string  original_path
+    function void set(string hdl_path, rggen_backdoor_vif vif);
+      string  path;
+      path                    = normalize_hdl_path(hdl_path);
+      this.vif_wrapper[path]  = new(vif);
+    endfunction
+
+    function rggen_backdoor_vif get(string hdl_path);
+      return vif_wrapper[hdl_path].vif;
+    endfunction
+`endif
+    protected function string normalize_hdl_path(string path);
+      string  normalized_path;
+      for (int i = 0;i < path.len();++i) begin
+        if ((path[i] != "\\") && (path[i] != " ")) begin
+          normalized_path = {normalized_path, path[i]};
+        end
+      end
+      return normalized_path.tolower();
+    endfunction
+
+    static  protected rggen_backdoor_if_store store;
+
+    static function rggen_backdoor_if_store get_store();
+      if (store == null) begin
+        store = new;
+      end
+      return store;
+    endfunction
+  endclass
+
+  function automatic void set_backdoor_vif(
+    string              hdl_path,
+    rggen_backdoor_vif  vif
   );
-    string  path;
-    path  = original_path;
-    if (path[0] == "\\") begin
-      path  = path.substr(1, path.len() - 1);
-    end
-    if (path[path.len()-1] == " ") begin
-      path  = path.substr(0, path.len() - 2);
-    end
-    return path.tolower();
+    rggen_backdoor_if_store store;
+    store = rggen_backdoor_if_store::get_store();
+    store.set(hdl_path, vif);
   endfunction
 
-  function automatic rggen_backdoor_vif get_backdoor_vif(
-    string  hdl_path
-  );
-    return backdoor_vif[hdl_path];
+  function automatic rggen_backdoor_vif get_backdoor_vif(string hdl_path);
+    rggen_backdoor_if_store store;
+    store = rggen_backdoor_if_store::get_store();
+    return store.get(hdl_path);
   endfunction
 endpackage
 `endif