diff --git a/src/security/key-chain.cpp b/src/security/key-chain.cpp
index d3e7a6a..75d3aaa 100644
--- a/src/security/key-chain.cpp
+++ b/src/security/key-chain.cpp
@@ -17,6 +17,7 @@
 
 using namespace std;
 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;