diff --git a/ndn-cpp/fields/signature.h b/ndn-cpp/fields/signature.h
index a9fb39a..1368663 100644
--- a/ndn-cpp/fields/signature.h
+++ b/ndn-cpp/fields/signature.h
@@ -12,11 +12,16 @@
 #define NDN_SIGNATURE_H
 
 #include <iostream>
+#include <boost/shared_ptr.hpp>
 
 namespace ndn {
 
 namespace wire { class Base; }
 
+class Signature;
+typedef boost::shared_ptr<Signature> SignaturePtr;
+typedef boost::shared_ptr<const Signature> ConstSignaturePtr;
+
 /**
  * @brief Pure virtual class providing an interface to work with signatures for NDN data packets
  */