diff --git a/tests/test-common.hpp b/tests/test-common.hpp
index c7b7c36..f5a309a 100644
--- a/tests/test-common.hpp
+++ b/tests/test-common.hpp
@@ -1,12 +1,12 @@
 /* -*- Mode:C++; c-file-style:"gnu"; indent-tabs-mode:nil; -*- */
 /**
- * Copyright (c) 2014,  Regents of the University of California,
- *                      Arizona Board of Regents,
- *                      Colorado State University,
- *                      University Pierre & Marie Curie, Sorbonne University,
- *                      Washington University in St. Louis,
- *                      Beijing Institute of Technology,
- *                      The University of Memphis
+ * Copyright (c) 2014-2015,  Regents of the University of California,
+ *                           Arizona Board of Regents,
+ *                           Colorado State University,
+ *                           University Pierre & Marie Curie, Sorbonne University,
+ *                           Washington University in St. Louis,
+ *                           Beijing Institute of Technology,
+ *                           The University of Memphis.
  *
  * This file is part of NFD (Named Data Networking Forwarding Daemon).
  * See AUTHORS.md for complete list of NFD authors and contributors.
@@ -62,7 +62,7 @@
 
 /** \brief a base test fixture that overrides steady clock and system clock
  */
-class UnitTestTimeFixture : public BaseFixture
+class UnitTestTimeFixture : public virtual BaseFixture
 {
 protected:
   UnitTestTimeFixture()