diff --git a/src/data.hpp b/src/data.hpp
index 70d1a72..1480103 100644
--- a/src/data.hpp
+++ b/src/data.hpp
@@ -321,6 +321,8 @@
   friend class nfd::LocalControlHeader;
 };
 
+std::ostream&
+operator<<(std::ostream& os, const Data& data);
 
 inline bool
 Data::hasWire() const
diff --git a/src/interest.cpp b/src/interest.cpp
index 986a5ec..a6bd107 100644
--- a/src/interest.cpp
+++ b/src/interest.cpp
@@ -255,7 +255,7 @@
   }
   if (interest.getInterestLifetime() >= time::milliseconds::zero()
       && interest.getInterestLifetime() != DEFAULT_INTEREST_LIFETIME) {
-    os << delim << "ndn.InterestLifetime=" << interest.getInterestLifetime();
+    os << delim << "ndn.InterestLifetime=" << interest.getInterestLifetime().count();
     delim = '&';
   }
 
diff --git a/tests/unit-tests/test-data.cpp b/tests/unit-tests/test-data.cpp
index e7be94e..5ce434e 100644
--- a/tests/unit-tests/test-data.cpp
+++ b/tests/unit-tests/test-data.cpp
@@ -348,6 +348,15 @@
 
   BOOST_REQUIRE_EQUAL_COLLECTIONS(Data1, Data1+sizeof(Data1),
                                   dataBlock.begin(), dataBlock.end());
+
+  std::ostringstream strStream;
+  BOOST_CHECK_NO_THROW(strStream << d);
+
+  BOOST_CHECK_EQUAL(strStream.str(),
+                    "Name: /local/ndn/prefix\n"
+                    "MetaInfo: ContentType: 0, FreshnessPeriod: 10000 milliseconds\n"
+                    "Content: (size: 8)\n"
+                    "Signature: (type: 1, value_length: 128)\n");
 }
 
 class DataIdentityFixture
diff --git a/tests/unit-tests/test-interest.cpp b/tests/unit-tests/test-interest.cpp
index f02a8a8..0b397cf 100644
--- a/tests/unit-tests/test-interest.cpp
+++ b/tests/unit-tests/test-interest.cpp
@@ -341,6 +341,16 @@
 
   BOOST_CHECK_EQUAL_COLLECTIONS(Interest2, Interest2 + sizeof(Interest2),
                                 wire.begin(), wire.end());
+
+  std::ostringstream strStream;
+  BOOST_CHECK_NO_THROW(strStream << i);
+
+  BOOST_CHECK_EQUAL(strStream.str(),
+                    "/local/ndn/prefix?"
+                    "ndn.MinSuffixComponents=1&ndn.MaxSuffixComponents=1&"
+                    "ndn.ChildSelector=1&ndn.Scope=1&"
+                    "ndn.InterestLifetime=1000&"
+                    "ndn.Nonce=2&ndn.Exclude=alex,xxxx,*,yyyy");
 }
 
 BOOST_AUTO_TEST_CASE(EncodeWithLocalHeader)