diff --git a/src/protocol-detail/challenge.hpp b/src/protocol-detail/challenge.hpp
index 23a9d84..a506346 100644
--- a/src/protocol-detail/challenge.hpp
+++ b/src/protocol-detail/challenge.hpp
@@ -36,7 +36,7 @@
   decodeDataContent(const Block& data, RequesterState& state);
 };
 
-}  // namespace ndncert
-}  // namespace ndn
+} // namespace ndncert
+} // namespace ndn
 
 #endif // NDNCERT_PROTOCOL_DETAIL_HPP
\ No newline at end of file