diff --git a/src/route/nexthop-list.hpp b/src/route/nexthop-list.hpp
index 9ba0772..577165f 100644
--- a/src/route/nexthop-list.hpp
+++ b/src/route/nexthop-list.hpp
@@ -1,6 +1,6 @@
 /* -*- Mode:C++; c-file-style:"gnu"; indent-tabs-mode:nil; -*- */
 /**
- * Copyright (c) 2014-2017,  The University of Memphis,
+ * Copyright (c) 2014-2018,  The University of Memphis,
  *                           Regents of the University of California
  *
  * This file is part of NLSR (Named-data Link State Routing).
@@ -87,8 +87,8 @@
     m_nexthopList.clear();
   }
 
-  std::set<NextHop, NextHopComparator>&
-  getNextHops()
+  const std::set<NextHop, NextHopComparator>&
+  getNextHops() const
   {
     return m_nexthopList;
   }