diff --git a/tests/unit/security/validation-error.t.cpp b/tests/unit/security/validation-error.t.cpp
index 6c1b5f7..c4a1a08 100644
--- a/tests/unit/security/validation-error.t.cpp
+++ b/tests/unit/security/validation-error.t.cpp
@@ -22,6 +22,7 @@
 #include "ndn-cxx/security/validation-error.hpp"
 
 #include "tests/boost-test.hpp"
+
 #include <boost/lexical_cast.hpp>
 
 namespace ndn {
@@ -37,17 +38,22 @@
   ValidationError e1{ValidationError::INVALID_SIGNATURE};
   BOOST_CHECK_EQUAL(e1.getCode(), 1);
   BOOST_CHECK_EQUAL(e1.getInfo(), "");
-  BOOST_CHECK_EQUAL(boost::lexical_cast<std::string>(e1), "Invalid signature");
+  BOOST_CHECK_EQUAL(boost::lexical_cast<std::string>(e1), "Signature verification failed");
 
-  ValidationError e2{ValidationError::NO_SIGNATURE, "message"};
+  ValidationError e2{ValidationError::MALFORMED_SIGNATURE, "message"};
   BOOST_CHECK_EQUAL(e2.getCode(), 2);
   BOOST_CHECK_EQUAL(e2.getInfo(), "message");
-  BOOST_CHECK_EQUAL(boost::lexical_cast<std::string>(e2), "Missing signature (message)");
+  BOOST_CHECK_EQUAL(boost::lexical_cast<std::string>(e2), "Missing or malformed signature (message)");
 
   ValidationError e3{65535, "other message"};
   BOOST_CHECK_EQUAL(e3.getCode(), 65535);
   BOOST_CHECK_EQUAL(e3.getInfo(), "other message");
   BOOST_CHECK_EQUAL(boost::lexical_cast<std::string>(e3), "Custom error code 65535 (other message)");
+
+  ValidationError e4{200};
+  BOOST_CHECK_EQUAL(e4.getCode(), 200);
+  BOOST_CHECK_EQUAL(e4.getInfo(), "");
+  BOOST_CHECK_EQUAL(boost::lexical_cast<std::string>(e4), "Unknown error code 200");
 }
 
 BOOST_AUTO_TEST_SUITE_END() // TestValidationError
diff --git a/tests/unit/security/validation-policy-command-interest.t.cpp b/tests/unit/security/validation-policy-command-interest.t.cpp
index d6fd74f..604c60d 100644
--- a/tests/unit/security/validation-policy-command-interest.t.cpp
+++ b/tests/unit/security/validation-policy-command-interest.t.cpp
@@ -165,7 +165,7 @@
   auto i1 = Interest("/short");
   BOOST_TEST_REQUIRE(i1.getName().size() < signed_interest::MIN_SIZE);
   VALIDATE_FAILURE(i1, "Should fail (not signed / name too short)");
-  BOOST_TEST(lastError.getCode() == ValidationError::NO_SIGNATURE);
+  BOOST_TEST(lastError.getCode() == ValidationError::MALFORMED_SIGNATURE);
 }
 
 BOOST_AUTO_TEST_CASE(BadSigInfo)
@@ -174,7 +174,7 @@
   setNameComponent(i1, command_interest::POS_SIG_INFO, "not-SignatureInfo");
   BOOST_TEST_REQUIRE(i1.getName().size() >= command_interest::MIN_SIZE);
   VALIDATE_FAILURE(i1, "Should fail (signature info is missing)");
-  BOOST_TEST(lastError.getCode() == ValidationError::NO_SIGNATURE);
+  BOOST_TEST(lastError.getCode() == ValidationError::MALFORMED_SIGNATURE);
 }
 
 BOOST_AUTO_TEST_CASE(BadTimestampV02)
diff --git a/tests/unit/security/validation-policy-simple-hierarchy.t.cpp b/tests/unit/security/validation-policy-simple-hierarchy.t.cpp
index 38ab30c..788a7c9 100644
--- a/tests/unit/security/validation-policy-simple-hierarchy.t.cpp
+++ b/tests/unit/security/validation-policy-simple-hierarchy.t.cpp
@@ -43,7 +43,7 @@
 
   auto packet = Packet::makePacket(name);
   VALIDATE_FAILURE(packet, "Unsigned");
-  BOOST_TEST((lastError.getCode() == ValidationError::NO_SIGNATURE ||        // Interest
+  BOOST_TEST((lastError.getCode() == ValidationError::MALFORMED_SIGNATURE || // Interest
               lastError.getCode() == ValidationError::INVALID_KEY_LOCATOR)); // Data
 
   packet = Packet::makePacket(name);
diff --git a/tests/unit/security/validator.t.cpp b/tests/unit/security/validator.t.cpp
index 842f2f5..d1b746b 100644
--- a/tests/unit/security/validator.t.cpp
+++ b/tests/unit/security/validator.t.cpp
@@ -64,7 +64,7 @@
   BOOST_REQUIRE_NO_THROW(interest.getSignatureValue());
 
   VALIDATE_FAILURE(interest, "InterestSignatureInfo decoding should fail");
-  BOOST_TEST(lastError.getCode() == ValidationError::NO_SIGNATURE);
+  BOOST_TEST(lastError.getCode() == ValidationError::MALFORMED_SIGNATURE);
   BOOST_TEST(face.sentInterests.size() == 0);
 }
 
@@ -259,7 +259,7 @@
   Data data("/Security/ValidatorFixture/Sub1/Sub2/Data");
 
   VALIDATE_FAILURE(interest, "Unsigned");
-  BOOST_TEST(lastError.getCode() == ValidationError::NO_SIGNATURE);
+  BOOST_TEST(lastError.getCode() == ValidationError::MALFORMED_SIGNATURE);
   VALIDATE_SUCCESS(data, "Policy bypasses validation for all data");
   BOOST_TEST(face.sentInterests.size() == 0);
   face.sentInterests.clear();