diff --git a/src/client-module.hpp b/src/client-module.hpp
index e285ce2..df2a43a 100644
--- a/src/client-module.hpp
+++ b/src/client-module.hpp
@@ -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.
  *
@@ -64,9 +64,11 @@
   using ErrorCallback = function<void (const std::string&)>;
 
 public:
-  explicit
   ClientModule(Face& face, security::v2::KeyChain& keyChain, size_t retryTimes = 2);
 
+  virtual
+  ~ClientModule();
+
   ClientConfig&
   getClientConf()
   {
@@ -176,7 +178,6 @@
   virtual void
   onNack(const Interest& interest, const lp::Nack& nack, const ErrorCallback& errorCallback);
 
-
 protected:
   ClientConfig m_config;
   Face& m_face;