diff --git a/compiler.h b/compiler.h
index cbd0e969f..85b908b87 100644
--- a/compiler.h
+++ b/compiler.h
@@ -100,6 +100,9 @@ extern bool warn_sens_entire_arr;
 /* Warn about level-appropriate anachronisms. */
 extern bool warn_anachronisms;
 
+/* Warn about nets that are references but not driven. */
+extern bool warn_floating_nets;
+
 /* This is true if verbose output is requested. */
 extern bool verbose_flag;
 
diff --git a/driver/main.c b/driver/main.c
index 048308206..810a2de90 100644
--- a/driver/main.c
+++ b/driver/main.c
@@ -503,6 +503,9 @@ static void process_warning_switch(const char*name)
       } else if (strcmp(name,"anachronisms") == 0) {
 	    if (! strchr(warning_flags, 'n'))
 		  strcat(warning_flags, "n");
+      } else if (strcmp(name,"floating-nets") == 0) {
+	    if (! strchr(warning_flags, 'f'))
+		  strcat(warning_flags, "f");
       } else if (strcmp(name,"implicit") == 0) {
 	    if (! strchr(warning_flags, 'i'))
 		  strcat(warning_flags, "i");
@@ -532,6 +535,12 @@ static void process_warning_switch(const char*name)
 		  cp[0] = cp[1];
 		  cp += 1;
 	    }
+      } else if (strcmp(name,"no-floating-nets") == 0) {
+	    char*cp = strchr(warning_flags, 'f');
+	    if (cp) while (*cp) {
+		  cp[0] = cp[1];
+		  cp += 1;
+	    }
       } else if (strcmp(name,"no-implicit") == 0) {
 	    char*cp = strchr(warning_flags, 'i');
 	    if (cp) while (*cp) {
diff --git a/main.cc b/main.cc
index 2e9dfdcfb..1b11f4f87 100644
--- a/main.cc
+++ b/main.cc
@@ -160,6 +160,7 @@ bool warn_ob_select = false;
 bool warn_sens_entire_vec = false;
 bool warn_sens_entire_arr = false;
 bool warn_anachronisms = false;
+bool warn_floating_nets = false;
 
 /*
  * Debug message class flags.
@@ -675,6 +676,9 @@ static void read_iconfig_file(const char*ipath)
 	    } else if (strcmp(buf,"warnings") == 0) {
 		    /* Scan the warnings enable string for warning flags. */
 		  for ( ;  *cp ;  cp += 1) switch (*cp) {
+		      case 'f':
+			warn_floating_nets = true;
+			break;
 		      case 'i':
 			warn_implicit = true;
 			break;
diff --git a/nodangle.cc b/nodangle.cc
index 3dcb32391..d02882a43 100644
--- a/nodangle.cc
+++ b/nodangle.cc
@@ -122,10 +122,61 @@ void nodangle_f::event(Design*, NetEvent*ev)
       }
 }
 
+static bool floating_net_tested(NetNet*sig)
+{
+      static set<NetNet*> tested_set;
+
+      pair< set<NetNet*>::iterator, bool > cur = tested_set.insert(sig);
+      return !cur.second;
+}
+
+static void check_is_floating(NetNet*sig)
+{
+      if (sig->type() == NetNet::SUPPLY0) return;
+      if (sig->type() == NetNet::SUPPLY1) return;
+      if (sig->type() == NetNet::TRI0) return;
+      if (sig->type() == NetNet::TRI1) return;
+      if (sig->type() == NetNet::IMPLICIT_REG) return;
+      if (sig->type() == NetNet::REG) return ;
+
+      if (sig->peek_lref() > 0) return;
+
+      for (unsigned idx = 0 ; idx < sig->pin_count() ; idx += 1) {
+	    if (sig->pin(idx).get_dir() == Link::OUTPUT)
+		  continue;
+
+	    if (sig->pin(idx).nexus()->drivers_present())
+		  continue;
+
+	    if (sig->port_type() == PortType::NOT_A_PORT && sig->pin_count()==1) {
+		  cerr << sig->get_fileline() << ": warning: "
+		       << "Signal " << scope_path(sig->scope())
+		       << "." << sig->name()
+		       << " has no drivers." << endl;
+	    } else if (sig->port_type()==PortType::NOT_A_PORT) {
+		  cerr << sig->get_fileline() << ": warning: "
+		       << "Signal " << scope_path(sig->scope())
+		       << "." << sig->name()
+		       << "[" << idx << "]"
+		       << " has no drivers." << endl;
+	    } else {
+		  cerr << sig->get_fileline() << ": warning: "
+		       << "Port " << sig->name()
+		       << " of " << scope_path(sig->scope())
+		       << " has no drivers." << endl;
+	    }
+      }
+
+}
+
 void nodangle_f::signal(Design*, NetNet*sig)
 {
       if (scomplete) return;
 
+      if (warn_floating_nets && !floating_net_tested(sig)) {
+	    check_is_floating(sig);
+      }
+
 	/* Cannot delete signals referenced in an expression
 	   or an l-value. */
       if (sig->get_refs() > 0)
diff --git a/scripts/devel-stub.conf b/scripts/devel-stub.conf
index 202c7eed5..def994a22 100644
--- a/scripts/devel-stub.conf
+++ b/scripts/devel-stub.conf
@@ -15,7 +15,7 @@ iwidth:32
 sys_func:vpi/system.sft
 sys_func:vpi/v2005_math.sft
 sys_func:vpi/va_math.sft
-warnings:ailnpstv
+warnings:afilnpstv
 debug:eval_tree
 debug:elaborate
 debug:emit