format update

Change-Id: I8e15451d7229cad5fb4c6d5cf7464fcde9d6c56c
diff --git a/src/ndncert-common.hpp b/src/ndncert-common.hpp
index 9bee44a..cf2643f 100644
--- a/src/ndncert-common.hpp
+++ b/src/ndncert-common.hpp
@@ -41,6 +41,7 @@
 #include <ndn-cxx/encoding/tlv.hpp>
 #include <ndn-cxx/data.hpp>
 #include <ndn-cxx/encoding/block.hpp>
+#include <ndn-cxx/encoding/block-helpers.hpp>
 #include <ndn-cxx/face.hpp>
 #include <ndn-cxx/interest.hpp>
 #include <ndn-cxx/link.hpp>