Need help with Dialog to Make Non-Modal

Code Snippet::::
SystemlogDialog::SystemlogDialog(int dummy)
{
  gtkbuilder = gtk_builder_new ();
  gtk_builder_add_from_file (gtkbuilder, "gtkbuilder.systemlogdialog.xml", NULL);

  Shortcuts shortcuts(0);

  dialog = GTK_WIDGET (gtk_builder_get_object (gtkbuilder, "dialog"));

  // Experimental - trying to make this window not modal, so it can float always to the side.
  gtk_window_set_modal(GTK_WINDOW(dialog), FALSE);

  textview = GTK_WIDGET (gtk_builder_get_object (gtkbuilder, "textview"));
  //gtk_widget_grab_focus(textview); // omitting this doesn't seem to change the modality of the window
...
setup of radio buttons, etc.

Snippet of gtkbuilder.systemlogdialog.xml::::
<?xml version="1.0"?>
<interface>
  <!-- interface-requires gtk+ 2.12 -->
  <!-- interface-naming-policy toplevel-contextual -->
  <object class="GtkDialog" id="dialog">
    <property name="height_request">480</property>
    <property name="border_width">5</property>
    <property name="title" translatable="yes">System log</property>
    <property name="resizable">True</property>
    <property name="modal">False</property>
    <property name="window_position">center</property>
    <property name="default_width">750</property>
    <property name="default_height">480</property>