diff --git a/src/pcsc.hxx b/src/pcsc.hxx
index bc1c6bb..d00bf5a 100644
--- a/src/pcsc.hxx
+++ b/src/pcsc.hxx
@@ -74,6 +74,7 @@
 #endif
 
 #ifdef NO_CXX2011
+#warning Old compiler (pre 2011): using boost as replacement for std
   #include <boost/shared_ptr.hpp>
   namespace std {
     template<class T> class shared_ptr: public boost::shared_ptr<T> {