diff --git a/ndn-cpp/common.h b/ndn-cpp/common.h
index 805be36..3ea8442 100644
--- a/ndn-cpp/common.h
+++ b/ndn-cpp/common.h
@@ -13,23 +13,24 @@
 #ifndef NDN_COMMON_H
 #define NDN_COMMON_H
 
-#include <boost/shared_ptr.hpp>
 #include <boost/make_shared.hpp>
 #include <boost/date_time/posix_time/posix_time_types.hpp>
 #include "../config.h"
 
-namespace ndn
-{
 // Depending on where ./configure found shared_ptr, define the ptr_lib namespace.
-// We always use ptr_lib::shared_ptr.
+// We always use ndn::ptr_lib::shared_ptr.
 #if HAVE_STD_SHARED_PTR
-namespace ptr_lib = std;
+#include <memory>
+namespace ndn { namespace ptr_lib = std; }
 #elif HAVE_BOOST_SHARED_PTR
-namespace ptr_lib = boost;
+#include <boost/shared_ptr.hpp>
+namespace ndn { namespace ptr_lib = boost; }
 #else
 #error "Can't find shared_ptr in std or boost"
 #endif
 
+namespace ndn
+{
 typedef boost::posix_time::ptime Time;
 typedef boost::posix_time::time_duration TimeInterval;