diff --git a/tgt-vvp/draw_ufunc.c b/tgt-vvp/draw_ufunc.c
index 83f4d2137..88fc519a5 100644
--- a/tgt-vvp/draw_ufunc.c
+++ b/tgt-vvp/draw_ufunc.c
@@ -65,6 +65,12 @@ static void function_argument_class(ivl_signal_t port, ivl_expr_t expr)
       fprintf(vvp_out, "    %%store/obj v%p_0;\n", port);
 }
 
+static void function_argument_string(ivl_signal_t port, ivl_expr_t expr)
+{
+      draw_eval_string(expr);
+      fprintf(vvp_out, "    %%store/str v%p_0;\n", port);
+}
+
 static void draw_function_argument(ivl_signal_t port, ivl_expr_t expr)
 {
       ivl_variable_type_t dtype = ivl_signal_data_type(port);
@@ -81,6 +87,9 @@ static void draw_function_argument(ivl_signal_t port, ivl_expr_t expr)
 	  case IVL_VT_CLASS:
 	    function_argument_class(port, expr);
 	    break;
+	  case IVL_VT_STRING:
+	    function_argument_string(port, expr);
+	    break;
 	  default:
 	    fprintf(stderr, "XXXX function argument %s type=%d?!\n",
 		    ivl_signal_basename(port), dtype);
diff --git a/vvp/vvp_net.cc b/vvp/vvp_net.cc
index 353a3fb7b..78b50145b 100644
--- a/vvp/vvp_net.cc
+++ b/vvp/vvp_net.cc
@@ -296,6 +296,11 @@ vvp_net_fil_t::prop_t vvp_net_fil_t::filter_long(long&)
       return PROP;
 }
 
+vvp_net_fil_t::prop_t vvp_net_fil_t::filter_string(const string&)
+{
+      return PROP;
+}
+
 vvp_net_fil_t::prop_t vvp_net_fil_t::filter_object(vvp_object_t&)
 {
       return PROP;
diff --git a/vvp/vvp_net.h b/vvp/vvp_net.h
index 27e4999d7..3554be58f 100644
--- a/vvp/vvp_net.h
+++ b/vvp/vvp_net.h
@@ -1229,6 +1229,7 @@ class vvp_net_fil_t  : public vvp_vpi_callback {
       virtual prop_t filter_real(double&val);
       virtual prop_t filter_long(long&val);
       virtual prop_t filter_object(vvp_object_t&val);
+      virtual prop_t filter_string(const std::string&val);
 
       virtual void release(vvp_net_ptr_t ptr, bool net_flag) =0;
       virtual void release_pv(vvp_net_ptr_t ptr, unsigned base, unsigned wid, bool net_flag) =0;
@@ -1708,7 +1709,9 @@ inline void vvp_net_t::send_real(double val, vvp_context_t context)
 
 inline void vvp_net_t::send_string(const std::string&val, vvp_context_t context)
 {
-      assert(!fil);
+      if (fil && !fil->filter_string(val))
+	    return;
+
       vvp_send_string(out_, val, context);
 }
 
diff --git a/vvp/vvp_net_sig.cc b/vvp/vvp_net_sig.cc
index b82d4ea0e..0e359367d 100644
--- a/vvp/vvp_net_sig.cc
+++ b/vvp/vvp_net_sig.cc
@@ -613,6 +613,11 @@ void vvp_fun_signal_string_sa::recv_string(vvp_net_ptr_t ptr, const std::string&
       }
 }
 
+const string& vvp_fun_signal_string_sa::get_string() const
+{
+      return value_;
+}
+
 vvp_fun_signal_string_aa::vvp_fun_signal_string_aa()
 {
       context_idx_ = vpip_add_item_to_context(this, vpip_peek_context_scope());
@@ -623,14 +628,41 @@ vvp_fun_signal_string_aa::~vvp_fun_signal_string_aa()
       assert(0);
 }
 
-void vvp_fun_signal_string_aa::alloc_instance(vvp_context_t)
+void vvp_fun_signal_string_aa::alloc_instance(vvp_context_t context)
 {
-      assert(0);
+      string*bits = new std::string;
+      vvp_set_context_item(context, context_idx_, bits);
+      *bits = "";
 }
 
-void vvp_fun_signal_string_aa::reset_instance(vvp_context_t)
+void vvp_fun_signal_string_aa::reset_instance(vvp_context_t context)
 {
-      assert(0);
+      string*bits = static_cast<std::string*>
+	    (vvp_get_context_item(context, context_idx_));
+      *bits = "";
+}
+
+#ifdef CHECK_WITH_VALGRIND
+void vvp_fun_signal_string_aa::free_instance(vvp_context_t context)
+{
+      string*bits = static_cast<std::string*>
+            (vvp_get_context_item(context, context_idx_));
+      delete bits;
+}
+#endif
+
+void vvp_fun_signal_string_aa::recv_string(vvp_net_ptr_t ptr, const std::string&bit, vvp_context_t context)
+{
+      assert(ptr.port() == 0);
+      assert(context);
+
+      string*bits = static_cast<std::string*>
+	    (vvp_get_context_item(context, context_idx_));
+
+      if (*bits != bit) {
+	    *bits = bit;
+	    ptr.ptr()->send_string(bit, context);
+      }
 }
 
 unsigned vvp_fun_signal_string_aa::value_size() const
@@ -662,6 +694,14 @@ double vvp_fun_signal_string_aa::real_value() const
       return 0.0;
 }
 
+const std::string& vvp_fun_signal_string_aa::get_string() const
+{
+      string*bits = static_cast<std::string*>
+            (vthread_get_rd_context_item(context_idx_));
+
+      return *bits;
+}
+
 void* vvp_fun_signal_string_aa::operator new(std::size_t size)
 {
       return vvp_net_fun_t::heap_.alloc(size);
diff --git a/vvp/vvp_net_sig.h b/vvp/vvp_net_sig.h
index cf45d944d..4c59f47ad 100644
--- a/vvp/vvp_net_sig.h
+++ b/vvp/vvp_net_sig.h
@@ -270,7 +270,7 @@ class vvp_fun_signal_string : public vvp_fun_signal_base {
 
       unsigned size() const { return 1; }
 
-      inline const std::string& get_string() const { return value_; }
+      virtual const std::string& get_string() const =0;
 
     protected:
       std::string value_;
@@ -286,6 +286,11 @@ class vvp_fun_signal_string_sa : public vvp_fun_signal_string {
 
       void recv_string(vvp_net_ptr_t port, const std::string&bit,
 		       vvp_context_t context);
+
+      const std::string& get_string() const;
+
+    private:
+      std::string value_;
 };
 
 /*
@@ -302,6 +307,8 @@ class vvp_fun_signal_string_aa : public vvp_fun_signal_string, public automatic_
 #ifdef CHECK_WITH_VALGRIND
       void free_instance(vvp_context_t context);
 #endif
+      void recv_string(vvp_net_ptr_t port, const std::string&bit,
+		       vvp_context_t context);
 
 	// Get information about the vector value.
       unsigned   value_size() const;
@@ -309,6 +316,7 @@ class vvp_fun_signal_string_aa : public vvp_fun_signal_string, public automatic_
       vvp_scalar_t scalar_value(unsigned idx) const;
       void vec4_value(vvp_vector4_t&) const;
       double real_value() const;
+      const std::string& get_string() const;
       void get_signal_value(struct t_vpi_value*vp);
 
     public: // These objects are only permallocated.