diff --git a/vhdlpp/parse.y b/vhdlpp/parse.y
index cc278f3ab..09c8e5f78 100644
--- a/vhdlpp/parse.y
+++ b/vhdlpp/parse.y
@@ -182,6 +182,16 @@ static list<VTypeRecord::element_t*>* record_elements(list<perm_string>*names,
       return res;
 }
 
+static void touchup_interface_for_functions(std::list<InterfacePort*>*ports)
+{
+      for (list<InterfacePort*>::iterator cur = ports->begin()
+		 ; cur != ports->end() ; ++cur) {
+	    InterfacePort*curp = *cur;
+	    if (curp->mode == PORT_NONE)
+		  curp->mode = PORT_IN;
+      }
+}
+
 %}
 
 
@@ -1152,6 +1162,7 @@ function_specification /* IEEE 1076-2008 P4.2.1 */
       { perm_string type_name = lex_strings.make($7);
 	perm_string name = lex_strings.make($2);
 	const VType*type_mark = active_scope->find_type(type_name);
+	touchup_interface_for_functions($4);
 	Subprogram*tmp = new Subprogram(name, $4, type_mark);
 	FILE_NAME(tmp,@1);
 	delete[]$2;
diff --git a/vhdlpp/subprogram_emit.cc b/vhdlpp/subprogram_emit.cc
index e70351a4c..efd586bd0 100644
--- a/vhdlpp/subprogram_emit.cc
+++ b/vhdlpp/subprogram_emit.cc
@@ -33,11 +33,34 @@ int Subprogram::emit_package(ostream&fd) const
 	    fd << "function ";
 	    return_type_->emit_def(fd);
 	    fd << " " << name_;
-	    fd << ";" << endl;
+	    fd << "(";
       } else {
 	    fd << "task " << name_ << ";" << endl;
       }
 
+      for (list<InterfacePort*>::const_iterator cur = ports_->begin()
+		 ; cur != ports_->end() ; ++cur) {
+	    if (cur != ports_->begin())
+		  fd << ", ";
+	    InterfacePort*curp = *cur;
+	    switch (curp->mode) {
+		case PORT_IN:
+		  fd << "input ";
+		  break;
+		case PORT_OUT:
+		  fd << "output ";
+		  break;
+		case PORT_NONE:
+		  fd << "inout /* PORT_NONE? */ ";
+		  break;
+	    }
+
+	    errors += curp->type->emit_def(fd);
+	    fd << " \\" << curp->name << " ";
+      }
+
+      fd << ");" << endl;
+
       if (statements_) {
 	    for (list<SequentialStmt*>::const_iterator cur = statements_->begin()
 		       ; cur != statements_->end() ; ++cur) {