diff --git a/conformance/conformance_test.cc b/conformance/conformance_test.cc
index 598ef732..d46fa877 100644
--- a/conformance/conformance_test.cc
+++ b/conformance/conformance_test.cc
@@ -272,11 +272,16 @@ void ConformanceTestSuite::RunValidInputTest(
   TestAllTypes test_message;
 
   switch (response.result_case()) {
+    case ConformanceResponse::RESULT_NOT_SET:
+      ReportFailure(test_name, request, response,
+                    "Response didn't have any field in the Response.");
+      return;
+
     case ConformanceResponse::kParseError:
     case ConformanceResponse::kRuntimeError:
     case ConformanceResponse::kSerializeError:
       ReportFailure(test_name, request, response,
-                    "Failed to parse JSON input or produce JSON output.");
+                    "Failed to parse input or produce output.");
       return;
 
     case ConformanceResponse::kSkipped:
@@ -400,6 +405,17 @@ void ConformanceTestSuite::RunValidJsonTestWithProtobufInput(
                     equivalent_text_format, conformance::JSON);
 }
 
+void ConformanceTestSuite::RunValidProtobufTest(
+    const string& test_name, const TestAllTypes& input,
+    const string& equivalent_text_format) {
+  RunValidInputTest("ProtobufInput." + test_name + ".ProtobufOutput",
+                    input.SerializeAsString(), conformance::PROTOBUF,
+                    equivalent_text_format, conformance::PROTOBUF);
+  RunValidInputTest("ProtobufInput." + test_name + ".JsonOutput",
+                    input.SerializeAsString(), conformance::PROTOBUF,
+                    equivalent_text_format, conformance::JSON);
+}
+
 // According to proto3 JSON specification, JSON serializers follow more strict
 // rules than parsers (e.g., a serializer must serialize int32 values as JSON
 // numbers while the parser is allowed to accept them as JSON strings). This
@@ -1225,6 +1241,34 @@ bool ConformanceTestSuite::RunSuite(ConformanceTestRunner* runner,
   ExpectParseFailureForJson(
       "OneofFieldDuplicate",
       R"({"oneofUint32": 1, "oneofString": "test"})");
+  // Ensure zero values for oneof make it out/backs.
+  {
+    TestAllTypes message;
+    message.set_oneof_uint32(0);
+    RunValidProtobufTest(
+        "OneofZeroUint32", message, "oneof_uint32: 0");
+    message.mutable_oneof_nested_message()->set_a(0);
+    RunValidProtobufTest(
+        "OneofZeroMessage", message, "oneof_nested_message: {}");
+    message.set_oneof_string("");
+    RunValidProtobufTest(
+        "OneofZeroString", message, "oneof_string: \"\"");
+    message.set_oneof_bytes("");
+    RunValidProtobufTest(
+        "OneofZeroBytes", message, "oneof_bytes: \"\"");
+  }
+  RunValidJsonTest(
+      "OneofZeroUint32",
+      R"({"oneofUint32": 0})", "oneof_uint32: 0");
+  RunValidJsonTest(
+      "OneofZeroMessage",
+      R"({"oneofNestedMessage": {}})", "oneof_nested_message: {}");
+  RunValidJsonTest(
+      "OneofZeroString",
+      R"({"oneofString": ""})", "oneof_string: \"\"");
+  RunValidJsonTest(
+      "OneofZeroBytes",
+      R"({"oneofBytes": ""})", "oneof_bytes: \"\"");
 
   // Repeated fields.
   RunValidJsonTest(
diff --git a/conformance/conformance_test.h b/conformance/conformance_test.h
index c9c5213c..56689318 100644
--- a/conformance/conformance_test.h
+++ b/conformance/conformance_test.h
@@ -133,6 +133,9 @@ class ConformanceTestSuite {
   void RunValidJsonTestWithProtobufInput(const string& test_name,
                                          const conformance::TestAllTypes& input,
                                          const string& equivalent_text_format);
+  void RunValidProtobufTest(const string& test_name,
+                            const conformance::TestAllTypes& input,
+                            const string& equivalent_text_format);
 
   typedef std::function<bool(const Json::Value&)> Validator;
   void RunValidJsonTestWithValidator(const string& test_name,
diff --git a/conformance/failure_list_objc.txt b/conformance/failure_list_objc.txt
index 5dac3501..ec7898cd 100644
--- a/conformance/failure_list_objc.txt
+++ b/conformance/failure_list_objc.txt
@@ -1,4 +1,6 @@
-# No tests currently failing.
+ProtobufInput.OneofZeroBytes.ProtobufOutput
+ProtobufInput.OneofZeroString.ProtobufOutput
+ProtobufInput.OneofZeroUint32.ProtobufOutput
 #
 # json input or output tests are skipped (in conformance_objc.m) as mobile
 # platforms don't support json wire format to avoid code bloat.
diff --git a/conformance/failure_list_python.txt b/conformance/failure_list_python.txt
index 550a043f..3918703a 100644
--- a/conformance/failure_list_python.txt
+++ b/conformance/failure_list_python.txt
@@ -35,6 +35,8 @@ JsonInput.Int32FieldMaxFloatValue.JsonOutput
 JsonInput.Int32FieldMaxFloatValue.ProtobufOutput
 JsonInput.Int32FieldMinFloatValue.JsonOutput
 JsonInput.Int32FieldMinFloatValue.ProtobufOutput
+JsonInput.OneofZeroMessage.JsonOutput
+JsonInput.OneofZeroMessage.ProtobufOutput
 JsonInput.OriginalProtoFieldName.JsonOutput
 JsonInput.OriginalProtoFieldName.ProtobufOutput
 JsonInput.RepeatedFieldWrongElementTypeExpectingIntegersGotBool
diff --git a/conformance/failure_list_python_cpp.txt b/conformance/failure_list_python_cpp.txt
index 1eb916ab..69746d9f 100644
--- a/conformance/failure_list_python_cpp.txt
+++ b/conformance/failure_list_python_cpp.txt
@@ -44,6 +44,8 @@ JsonInput.Int32FieldMaxFloatValue.JsonOutput
 JsonInput.Int32FieldMaxFloatValue.ProtobufOutput
 JsonInput.Int32FieldMinFloatValue.JsonOutput
 JsonInput.Int32FieldMinFloatValue.ProtobufOutput
+JsonInput.OneofZeroMessage.JsonOutput
+JsonInput.OneofZeroMessage.ProtobufOutput
 JsonInput.OriginalProtoFieldName.JsonOutput
 JsonInput.OriginalProtoFieldName.ProtobufOutput
 JsonInput.RepeatedFieldWrongElementTypeExpectingIntegersGotBool
diff --git a/conformance/failure_list_ruby.txt b/conformance/failure_list_ruby.txt
index 7c12da06..526c2e75 100644
--- a/conformance/failure_list_ruby.txt
+++ b/conformance/failure_list_ruby.txt
@@ -103,6 +103,8 @@ JsonInput.MessageMapField.JsonOutput
 JsonInput.MessageMapField.ProtobufOutput
 JsonInput.MessageRepeatedField.JsonOutput
 JsonInput.MessageRepeatedField.ProtobufOutput
+JsonInput.OneofZeroUint32.JsonOutput
+JsonInput.OneofZeroUint32.ProtobufOutput
 JsonInput.OptionalBoolWrapper.JsonOutput
 JsonInput.OptionalBoolWrapper.ProtobufOutput
 JsonInput.OptionalBytesWrapper.JsonOutput