diff --git a/model/ndn-content-object.h b/model/ndn-content-object.h
index c79ddf9..58e88a3 100644
--- a/model/ndn-content-object.h
+++ b/model/ndn-content-object.h
@@ -190,6 +190,13 @@
   mutable Ptr<const Packet> m_wire;
 };
 
+inline std::ostream &
+operator << (std::ostream &os, const ContentObject &d)
+{
+  d.Print (os);
+  return os;
+}
+
 /**
  * @ingroup ndn-exceptions
  * @brief Class for ContentObject parsing exception