diff --git a/tools/nfdc/find-face.hpp b/tools/nfdc/find-face.hpp
index 120718b..68e5f7b 100644
--- a/tools/nfdc/find-face.hpp
+++ b/tools/nfdc/find-face.hpp
@@ -1,6 +1,6 @@
 /* -*- Mode:C++; c-file-style:"gnu"; indent-tabs-mode:nil; -*- */
-/**
- * Copyright (c) 2014-2017,  Regents of the University of California,
+/*
+ * Copyright (c) 2014-2018,  Regents of the University of California,
  *                           Arizona Board of Regents,
  *                           Colorado State University,
  *                           University Pierre & Marie Curie, Sorbonne University,
@@ -125,7 +125,7 @@
    *  \return canonical FaceUri if canonization succeeds, input if canonization is unsupported
    *  \retval nullopt canonization fails; m_errorReason describes the failure
    */
-  ndn::optional<FaceUri>
+  optional<FaceUri>
   canonize(const std::string& fieldName, const FaceUri& input);
 
   /** \brief retrieve FaceStatus from filter