diff --git a/elaborate.cc b/elaborate.cc
index f22e38f00..ad7c273ab 100644
--- a/elaborate.cc
+++ b/elaborate.cc
@@ -944,6 +944,17 @@ NetNet*PGModule::resize_net_to_port_(Design*des, NetScope*scope,
       return tmp;
 }
 
+static bool need_bufz_for_input_port(const svector<NetNet*>&prts)
+{
+      if (prts[0]->port_type() != NetNet::PINPUT)
+	    return false;
+
+      if (prts[0]->pin(0).nexus()->drivers_present())
+	    return true;
+
+      return false;
+}
+
 /*
  * Instantiate a module by recursively elaborating it. Set the path of
  * the recursive elaboration so that signal names get properly
@@ -1162,7 +1173,7 @@ void PGModule::elaborate_mod_(Design*des, Module*rmod, NetScope*scope) const
 		       width. We use that, then, to decide how to hook
 		       it up.
 
-		       NOTE that this also handles the case that the
+v		       NOTE that this also handles the case that the
 		       port is actually empty on the inside. We assume
 		       in that case that the port is input. */
 
@@ -1176,6 +1187,21 @@ void PGModule::elaborate_mod_(Design*des, Module*rmod, NetScope*scope) const
 			continue;
 		  }
 
+		  if (need_bufz_for_input_port(prts)) {
+			NetBUFZ*tmp = new NetBUFZ(scope, scope->local_symbol(),
+						  sig->vector_width());
+			des->add_node(tmp);
+			connect(tmp->pin(1), sig->pin(0));
+
+			NetNet*tmp2 = new NetNet(scope, scope->local_symbol(),
+						 NetNet::WIRE, sig->vector_width());
+			tmp2->local_flag(true);
+			tmp2->set_line(*this);
+			tmp2->data_type(sig->data_type());
+			connect(tmp->pin(0), tmp2->pin(0));
+			sig = tmp2;
+		  }
+
 	    } else if (prts[0]->port_type() == NetNet::PINOUT) {
 
 		    /* Inout to/from module. This is a more
diff --git a/net_link.cc b/net_link.cc
index 228add8c0..5b2621b90 100644
--- a/net_link.cc
+++ b/net_link.cc
@@ -247,6 +247,41 @@ verinum::V Nexus::get_init() const
       return verinum::Vz;
 }
 
+bool Nexus::drivers_present() const
+{
+      assert(list_);
+      for (Link*cur = list_ ;  cur ; cur = cur->next_) {
+	    if (cur->get_dir() == Link::OUTPUT)
+		  return true;
+
+	    if (cur->get_dir() == Link::INPUT)
+		  continue;
+
+	      // Must be PASSIVE, so if it is some kind of net, see if
+	      // it is the sort that might drive the nexus.
+	    const NetObj*obj;
+	    unsigned pin;
+	    cur->cur_link(obj, pin);
+	    if (const NetNet*net = dynamic_cast<const NetNet*>(obj))
+		  switch (net->type()) {
+		      case NetNet::SUPPLY0:
+		      case NetNet::SUPPLY1:
+		      case NetNet::TRI0:
+		      case NetNet::TRI1:
+		      case NetNet::WAND:
+		      case NetNet::WOR:
+		      case NetNet::TRIAND:
+		      case NetNet::TRIOR:
+		      case NetNet::REG:
+			return true;
+		      default:
+			break;
+		  }
+      }
+
+      return false;
+}
+
 void Nexus::drivers_delays(NetExpr*rise, NetExpr*fall, NetExpr*decay)
 {
       for (Link*cur = list_ ; cur ; cur = cur->next_) {
diff --git a/netlist.h b/netlist.h
index d6e01bab2..7818938e8 100644
--- a/netlist.h
+++ b/netlist.h
@@ -290,6 +290,10 @@ class Nexus {
 
       NetNet* pick_any_net();
 
+	/* This method returns true if there are any drivers
+	   (including variables) attached to this nexus. */
+      bool drivers_present() const;
+
 	/* This method returns true if all the possible drivers of
 	   this nexus are constant. It will also return true if there
 	   are no drivers at all. */
diff --git a/vpi/sys_scanf.c b/vpi/sys_scanf.c
index c2b9a4898..aff54193f 100644
--- a/vpi/sys_scanf.c
+++ b/vpi/sys_scanf.c
@@ -281,7 +281,6 @@ static int scan_format(vpiHandle sys, struct byte_source*src, vpiHandle argv)
 		  int suppress_flag = 0;
 		  int length_field = -1;
 		  int code = 0;
-		  int sign_flag = 1;
 		  PLI_INT32 value;
 
 		  char*tmp;
@@ -373,30 +372,38 @@ static int scan_format(vpiHandle sys, struct byte_source*src, vpiHandle argv)
 			break;
 
 		      case 'd':
-			match_fail = 1;
-			  /* Decimal integer */
-			ch = byte_getc(src);
-			if (ch == '-') {
-			      sign_flag = -1;
-			      ch = byte_getc(src);
-			}
+			  /* decimal integer */
+			tmp = malloc(2);
 			value = 0;
-			while ( isdigit(ch) ) {
+			tmp[0] = 0;
+			match_fail = 1;
+
+			ch = byte_getc(src);
+			while (isdigit(ch) || ch == '_' || (value == 0 && ch == '-')) {
 			      match_fail = 0;
-			      value *= 10;
-			      value += ch - '0';
-			      ch = byte_getc(src);
+			      if (ch != '_') {
+			            tmp[value++] = ch;
+			            tmp = realloc(tmp, value+1);
+			            tmp[value] = 0;
+			            ch = byte_getc(src);
+			      }
+			}
+			byte_ungetc(src, ch);
+
+			if (match_fail) {
+			      free(tmp);
+			      break;
 			}
 
-			if (match_fail)
-			      break;
-
+			  /* Matched a decimal value, put it to an argument. */
 			item = vpi_scan(argv);
 			assert(item);
 
-			val.format = vpiIntVal;
-			val.value.integer = value * sign_flag;
+			val.format = vpiDecStrVal;
+			val.value.str = tmp;
 			vpi_put_value(item, &val, 0, vpiNoDelay);
+
+			free(tmp);
 			rc += 1;
 			break;
 
diff --git a/vvp/vpip_to_dec.cc b/vvp/vpip_to_dec.cc
index 782c31c0c..50d76a9ac 100644
--- a/vvp/vpip_to_dec.cc
+++ b/vvp/vpip_to_dec.cc
@@ -229,7 +229,13 @@ void vpip_dec_str_to_vec4(vvp_vector4_t&vec,
 	   input is "1234", str gets "4321". */
       unsigned slen = strlen(buf);
       char*str = new char[slen + 1];
+      int is_negative = 0;
       for (unsigned idx = 0 ;  idx < slen ;  idx += 1) {
+	    if (idx == slen-1 && buf[slen-idx-1] == '-') {
+	          is_negative = 1;
+		  slen--;
+		  continue;
+	    }
 	    if (isdigit(buf[slen-idx-1]))
 		  str[idx] = buf[slen-idx-1];
             else
@@ -266,5 +272,10 @@ void vpip_dec_str_to_vec4(vvp_vector4_t&vec,
 
       }
 
+      if (is_negative) {
+            vec.invert();
+            vec += 1;
+      }
+
       delete[]str;
 }