diff --git a/daemon/fw/forwarder.hpp b/daemon/fw/forwarder.hpp
index fca81eb..b0cc156 100644
--- a/daemon/fw/forwarder.hpp
+++ b/daemon/fw/forwarder.hpp
@@ -1,6 +1,6 @@
 /* -*- Mode:C++; c-file-style:"gnu"; indent-tabs-mode:nil; -*- */
 /**
- * Copyright (c) 2014-2016,  Regents of the University of California,
+ * Copyright (c) 2014-2017,  Regents of the University of California,
  *                           Arizona Board of Regents,
  *                           Colorado State University,
  *                           University Pierre & Marie Curie, Sorbonne University,
@@ -216,7 +216,7 @@
    */
   VIRTUAL_WITH_TESTS void
   onInterestFinalize(const shared_ptr<pit::Entry>& pitEntry, bool isSatisfied,
-                     time::milliseconds dataFreshnessPeriod = time::milliseconds(-1));
+                     ndn::optional<time::milliseconds> dataFreshnessPeriod = ndn::nullopt);
 
   /** \brief incoming Data pipeline
    */
@@ -249,7 +249,7 @@
 
   VIRTUAL_WITH_TESTS void
   setStragglerTimer(const shared_ptr<pit::Entry>& pitEntry, bool isSatisfied,
-                    time::milliseconds dataFreshnessPeriod = time::milliseconds(-1));
+                    ndn::optional<time::milliseconds> dataFreshnessPeriod = ndn::nullopt);
 
   VIRTUAL_WITH_TESTS void
   cancelUnsatisfyAndStragglerTimer(pit::Entry& pitEntry);
@@ -260,7 +260,7 @@
    */
   VIRTUAL_WITH_TESTS void
   insertDeadNonceList(pit::Entry& pitEntry, bool isSatisfied,
-                      time::milliseconds dataFreshnessPeriod, Face* upstream);
+                      ndn::optional<time::milliseconds> dataFreshnessPeriod, Face* upstream);
 
   /** \brief call trigger (method) on the effective strategy of pitEntry
    */