diff --git a/include/ndn-cpp/signature.hpp b/include/ndn-cpp/signature.hpp
index dcc0cf0..e38ad3e 100644
--- a/include/ndn-cpp/signature.hpp
+++ b/include/ndn-cpp/signature.hpp
@@ -27,7 +27,7 @@
   {
   }
   
-  Signature(const Block &info, const Block &value)
+  Signature(const Block &info, const Block &value = Block())
     : value_(value)
   {
     setInfo(info);