diff --git a/src/pcsc.hxx b/src/pcsc.hxx
index 5b2159e..bc1c6bb 100644
--- a/src/pcsc.hxx
+++ b/src/pcsc.hxx
@@ -73,7 +73,7 @@
   }
 #endif
 
-#if __cplusplus <= 199711L
+#ifdef NO_CXX2011
   #include <boost/shared_ptr.hpp>
   namespace std {
     template<class T> class shared_ptr: public boost::shared_ptr<T> {