diff --git a/src/requester-state.hpp b/src/requester-state.hpp
index fed7743..a6f1028 100644
--- a/src/requester-state.hpp
+++ b/src/requester-state.hpp
@@ -27,6 +27,7 @@
 
 namespace ndn {
 namespace ndncert {
+namespace requester {
 
 struct RequesterState {
   explicit
@@ -99,6 +100,7 @@
   bool m_isNewlyCreatedKey = false;
 };
 
+} // namespace requester
 } // namespace ndncert
 } // namespace ndn