diff --git a/src/detail/ndncert-common.hpp b/src/detail/ndncert-common.hpp
index 77f6ca2..0e1b392 100644
--- a/src/detail/ndncert-common.hpp
+++ b/src/detail/ndncert-common.hpp
@@ -48,6 +48,7 @@
 #include <ndn-cxx/security/certificate.hpp>
 #include <ndn-cxx/security/key-chain.hpp>
 #include <ndn-cxx/util/logger.hpp>
+#include <ndn-cxx/util/nonstd/optional.hpp>
 #include <tuple>
 #include <boost/algorithm/string.hpp>
 #include <boost/assert.hpp>