diff --git a/src/security/tpm/back-end-osx.hpp b/src/security/tpm/back-end-osx.hpp
index 61f7f68..bb018be 100644
--- a/src/security/tpm/back-end-osx.hpp
+++ b/src/security/tpm/back-end-osx.hpp
@@ -1,6 +1,6 @@
 /* -*- Mode:C++; c-file-style:"gnu"; indent-tabs-mode:nil; -*- */
 /*
- * Copyright (c) 2013-2017 Regents of the University of California.
+ * Copyright (c) 2013-2018 Regents of the University of California.
  *
  * This file is part of ndn-cxx library (NDN C++ library with eXperimental eXtensions).
  *
@@ -39,17 +39,6 @@
 class BackEndOsx : public BackEnd
 {
 public:
-  class Error : public BackEnd::Error
-  {
-  public:
-    explicit
-    Error(const std::string& what)
-      : BackEnd::Error(what)
-    {
-    }
-  };
-
-public:
   /**
    * @brief Create TPM backed based on macOS KeyChain service
    * @param location Not used (required by the TPM-registration interface)