diff --git a/src/security/key-chain.cpp b/src/security/key-chain.cpp
index 75d3aaa..e3980a9 100644
--- a/src/security/key-chain.cpp
+++ b/src/security/key-chain.cpp
@@ -19,8 +19,8 @@
 using namespace ndn::ptr_lib;
 using namespace ndn::func_lib;
 #if NDN_CPP_HAVE_STD_FUNCTION
-// In the std library, the placeholders are in a different namespace than boost.                                    
-using namespace func_lib::placeholders;
+// In the std library, the placeholders are in a different namespace than boost.
+using namespace ndn::func_lib::placeholders;
 #endif
 
 namespace ndn {