diff --git a/src/challenge-module.cpp b/src/challenge-module.cpp
index 224a30c..c1f3432 100644
--- a/src/challenge-module.cpp
+++ b/src/challenge-module.cpp
@@ -1,6 +1,6 @@
 /* -*- Mode:C++; c-file-style:"gnu"; indent-tabs-mode:nil; -*- */
 /**
- * Copyright (c) 2017, Regents of the University of California.
+ * Copyright (c) 2017-2018, Regents of the University of California.
  *
  * This file is part of ndncert, a certificate management system based on NDN.
  *
@@ -37,6 +37,8 @@
 {
 }
 
+ChallengeModule::~ChallengeModule() = default;
+
 unique_ptr<ChallengeModule>
 ChallengeModule::createChallengeModule(const std::string& canonicalName)
 {