return g_string_free (string, FALSE);
 }
 
+#endif // wxUSE_STACKWALKER
+
 void gtk_assert_dialog_set_message(GtkAssertDialog *dlg, const gchar *msg)
 {
     /* prepend and append the <b> tag
     g_free (escaped_msg);
 }
 
+#if wxUSE_STACKWALKER
+
 void gtk_assert_dialog_set_backtrace_callback(GtkAssertDialog *assertdlg,
                                               GtkAssertDialogStackFrameCallback callback,
                                               void *userdata)