diff --git a/elab_sig.cc b/elab_sig.cc
index e7169fed0..2e046ac69 100644
--- a/elab_sig.cc
+++ b/elab_sig.cc
@@ -17,7 +17,7 @@
  *    Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA
  */
 #if !defined(WINNT) && !defined(macintosh)
-#ident "$Id: elab_sig.cc,v 1.18 2001/12/03 04:47:14 steve Exp $"
+#ident "$Id: elab_sig.cc,v 1.19 2002/01/23 03:35:17 steve Exp $"
 #endif
 
 # include "config.h"
@@ -237,6 +237,17 @@ void PFunction::elaborate_sig(Design*des, NetScope*scope) const
       string fname = scope->basename();
       assert(scope->type() == NetScope::FUNC);
 
+	/* Make sure the function has at least one input port. If it
+	   fails this test, print an error message. Keep going so we
+	   can find more errors. */
+      if (ports_ == 0) {
+	    cerr << get_line() << ": error: Function " << fname
+		 << " has no ports." << endl;
+	    cerr << get_line() << ":      : Functions must have"
+		 << " at least one input port." << endl;
+	    des->errors += 1;
+      }
+
       svector<NetNet*>ports (ports_? ports_->count()+1 : 1);
 
 	/* Get the reg for the return value. I know the name of the
@@ -484,6 +495,9 @@ void PWire::elaborate_sig(Design*des, NetScope*scope) const
 
 /*
  * $Log: elab_sig.cc,v $
+ * Revision 1.19  2002/01/23 03:35:17  steve
+ *  Detect incorrect function ports.
+ *
  * Revision 1.18  2001/12/03 04:47:14  steve
  *  Parser and pform use hierarchical names as hname_t
  *  objects instead of encoded strings.
diff --git a/parse.y b/parse.y
index 4488516e4..899f3c97d 100644
--- a/parse.y
+++ b/parse.y
@@ -19,7 +19,7 @@
  *    Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA
  */
 #if !defined(WINNT) && !defined(macintosh)
-#ident "$Id: parse.y,v 1.144 2002/01/12 04:03:39 steve Exp $"
+#ident "$Id: parse.y,v 1.145 2002/01/23 03:35:17 steve Exp $"
 #endif
 
 # include "config.h"
@@ -900,6 +900,20 @@ function_item
 						@1.text, @1.first_line);
 		  $$ = tmp;
 		}
+	| K_output range_opt list_of_variables ';'
+                { svector<PWire*>*tmp
+			= pform_make_task_ports(NetNet::PINPUT, $2, $3,
+						@1.text, @1.first_line);
+		  $$ = tmp;
+		  yyerror(@1, "Functions may not have output ports.");
+		}
+	| K_inout range_opt list_of_variables ';'
+                { svector<PWire*>*tmp
+			= pform_make_task_ports(NetNet::PINPUT, $2, $3,
+						@1.text, @1.first_line);
+		  $$ = tmp;
+		  yyerror(@1, "Functions may not have inout ports.");
+		}
 	| block_item_decl
                 { $$ = 0; }
 	;