diff --git a/csharp/src/Google.Protobuf.Test.TestProtos/UnittestIssues.cs b/csharp/src/Google.Protobuf.Test.TestProtos/UnittestIssues.cs
index ec4c07b112..3440105514 100644
--- a/csharp/src/Google.Protobuf.Test.TestProtos/UnittestIssues.cs
+++ b/csharp/src/Google.Protobuf.Test.TestProtos/UnittestIssues.cs
@@ -54,11 +54,13 @@ namespace UnitTest.Issues.TestProtos {
             "dEluT25lb2YSLgoKbnVsbF92YWx1ZRgCIAEoDjIaLmdvb2dsZS5wcm90b2J1",
             "Zi5OdWxsVmFsdWUiYAoXTWl4ZWRSZWd1bGFyQW5kT3B0aW9uYWwSFQoNcmVn",
             "dWxhcl9maWVsZBgBIAEoCRIbCg5vcHRpb25hbF9maWVsZBgCIAEoCUgAiAEB",
-            "QhEKD19vcHRpb25hbF9maWVsZCpVCgxOZWdhdGl2ZUVudW0SFgoSTkVHQVRJ",
-            "VkVfRU5VTV9aRVJPEAASFgoJRml2ZUJlbG93EPv//////////wESFQoITWlu",
-            "dXNPbmUQ////////////ASouCg5EZXByZWNhdGVkRW51bRITCg9ERVBSRUNB",
-            "VEVEX1pFUk8QABIHCgNvbmUQAUIdqgIaVW5pdFRlc3QuSXNzdWVzLlRlc3RQ",
-            "cm90b3NiBnByb3RvMw=="));
+            "QhEKD19vcHRpb25hbF9maWVsZCI5ChJPbmVvZldpdGhOb25lRmllbGQSCwoB",
+            "eBgBIAEoCUgAEg4KBG5vbmUYAiABKAlIAEIGCgR0ZXN0IjUKEU9uZW9mV2l0",
+            "aE5vbmVOYW1lEgsKAXgYASABKAlIABILCgF5GAIgASgJSABCBgoEbm9uZSpV",
+            "CgxOZWdhdGl2ZUVudW0SFgoSTkVHQVRJVkVfRU5VTV9aRVJPEAASFgoJRml2",
+            "ZUJlbG93EPv//////////wESFQoITWludXNPbmUQ////////////ASouCg5E",
+            "ZXByZWNhdGVkRW51bRITCg9ERVBSRUNBVEVEX1pFUk8QABIHCgNvbmUQAUId",
+            "qgIaVW5pdFRlc3QuSXNzdWVzLlRlc3RQcm90b3NiBnByb3RvMw=="));
       descriptor = pbr::FileDescriptor.FromGeneratedCode(descriptorData,
           new pbr::FileDescriptor[] { global::Google.Protobuf.WellKnownTypes.StructReflection.Descriptor, },
           new pbr::GeneratedClrTypeInfo(new[] {typeof(global::UnitTest.Issues.TestProtos.NegativeEnum), typeof(global::UnitTest.Issues.TestProtos.DeprecatedEnum), }, null, new pbr::GeneratedClrTypeInfo[] {
@@ -73,7 +75,9 @@ namespace UnitTest.Issues.TestProtos {
             new pbr::GeneratedClrTypeInfo(typeof(global::UnitTest.Issues.TestProtos.OneofMerging), global::UnitTest.Issues.TestProtos.OneofMerging.Parser, new[]{ "Text", "Nested" }, new[]{ "Value" }, null, null, new pbr::GeneratedClrTypeInfo[] { new pbr::GeneratedClrTypeInfo(typeof(global::UnitTest.Issues.TestProtos.OneofMerging.Types.Nested), global::UnitTest.Issues.TestProtos.OneofMerging.Types.Nested.Parser, new[]{ "X", "Y" }, null, null, null, null)}),
             new pbr::GeneratedClrTypeInfo(typeof(global::UnitTest.Issues.TestProtos.NullValueOutsideStruct), global::UnitTest.Issues.TestProtos.NullValueOutsideStruct.Parser, new[]{ "StringValue", "NullValue" }, new[]{ "Value" }, null, null, null),
             new pbr::GeneratedClrTypeInfo(typeof(global::UnitTest.Issues.TestProtos.NullValueNotInOneof), global::UnitTest.Issues.TestProtos.NullValueNotInOneof.Parser, new[]{ "NullValue" }, null, null, null, null),
-            new pbr::GeneratedClrTypeInfo(typeof(global::UnitTest.Issues.TestProtos.MixedRegularAndOptional), global::UnitTest.Issues.TestProtos.MixedRegularAndOptional.Parser, new[]{ "RegularField", "OptionalField" }, new[]{ "OptionalField" }, null, null, null)
+            new pbr::GeneratedClrTypeInfo(typeof(global::UnitTest.Issues.TestProtos.MixedRegularAndOptional), global::UnitTest.Issues.TestProtos.MixedRegularAndOptional.Parser, new[]{ "RegularField", "OptionalField" }, new[]{ "OptionalField" }, null, null, null),
+            new pbr::GeneratedClrTypeInfo(typeof(global::UnitTest.Issues.TestProtos.OneofWithNoneField), global::UnitTest.Issues.TestProtos.OneofWithNoneField.Parser, new[]{ "X", "None" }, new[]{ "Test" }, null, null, null),
+            new pbr::GeneratedClrTypeInfo(typeof(global::UnitTest.Issues.TestProtos.OneofWithNoneName), global::UnitTest.Issues.TestProtos.OneofWithNoneName.Parser, new[]{ "X", "Y" }, new[]{ "None" }, null, null, null)
           }));
     }
     #endregion
@@ -3825,6 +3829,524 @@ namespace UnitTest.Issues.TestProtos {
 
   }
 
+  public sealed partial class OneofWithNoneField : pb::IMessage<OneofWithNoneField>
+  #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
+      , pb::IBufferMessage
+  #endif
+  {
+    private static readonly pb::MessageParser<OneofWithNoneField> _parser = new pb::MessageParser<OneofWithNoneField>(() => new OneofWithNoneField());
+    private pb::UnknownFieldSet _unknownFields;
+    [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
+    [global::System.CodeDom.Compiler.GeneratedCode("protoc", null)]
+    public static pb::MessageParser<OneofWithNoneField> Parser { get { return _parser; } }
+
+    [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
+    [global::System.CodeDom.Compiler.GeneratedCode("protoc", null)]
+    public static pbr::MessageDescriptor Descriptor {
+      get { return global::UnitTest.Issues.TestProtos.UnittestIssuesReflection.Descriptor.MessageTypes[12]; }
+    }
+
+    [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
+    [global::System.CodeDom.Compiler.GeneratedCode("protoc", null)]
+    pbr::MessageDescriptor pb::IMessage.Descriptor {
+      get { return Descriptor; }
+    }
+
+    [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
+    [global::System.CodeDom.Compiler.GeneratedCode("protoc", null)]
+    public OneofWithNoneField() {
+      OnConstruction();
+    }
+
+    partial void OnConstruction();
+
+    [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
+    [global::System.CodeDom.Compiler.GeneratedCode("protoc", null)]
+    public OneofWithNoneField(OneofWithNoneField other) : this() {
+      switch (other.TestCase) {
+        case TestOneofCase.X:
+          X = other.X;
+          break;
+        case TestOneofCase.None_:
+          None = other.None;
+          break;
+      }
+
+      _unknownFields = pb::UnknownFieldSet.Clone(other._unknownFields);
+    }
+
+    [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
+    [global::System.CodeDom.Compiler.GeneratedCode("protoc", null)]
+    public OneofWithNoneField Clone() {
+      return new OneofWithNoneField(this);
+    }
+
+    /// <summary>Field number for the "x" field.</summary>
+    public const int XFieldNumber = 1;
+    [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
+    [global::System.CodeDom.Compiler.GeneratedCode("protoc", null)]
+    public string X {
+      get { return testCase_ == TestOneofCase.X ? (string) test_ : ""; }
+      set {
+        test_ = pb::ProtoPreconditions.CheckNotNull(value, "value");
+        testCase_ = TestOneofCase.X;
+      }
+    }
+
+    /// <summary>Field number for the "none" field.</summary>
+    public const int NoneFieldNumber = 2;
+    [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
+    [global::System.CodeDom.Compiler.GeneratedCode("protoc", null)]
+    public string None {
+      get { return testCase_ == TestOneofCase.None_ ? (string) test_ : ""; }
+      set {
+        test_ = pb::ProtoPreconditions.CheckNotNull(value, "value");
+        testCase_ = TestOneofCase.None_;
+      }
+    }
+
+    private object test_;
+    /// <summary>Enum of possible cases for the "test" oneof.</summary>
+    public enum TestOneofCase {
+      None = 0,
+      X = 1,
+      None_ = 2,
+    }
+    private TestOneofCase testCase_ = TestOneofCase.None;
+    [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
+    [global::System.CodeDom.Compiler.GeneratedCode("protoc", null)]
+    public TestOneofCase TestCase {
+      get { return testCase_; }
+    }
+
+    [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
+    [global::System.CodeDom.Compiler.GeneratedCode("protoc", null)]
+    public void ClearTest() {
+      testCase_ = TestOneofCase.None;
+      test_ = null;
+    }
+
+    [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
+    [global::System.CodeDom.Compiler.GeneratedCode("protoc", null)]
+    public override bool Equals(object other) {
+      return Equals(other as OneofWithNoneField);
+    }
+
+    [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
+    [global::System.CodeDom.Compiler.GeneratedCode("protoc", null)]
+    public bool Equals(OneofWithNoneField other) {
+      if (ReferenceEquals(other, null)) {
+        return false;
+      }
+      if (ReferenceEquals(other, this)) {
+        return true;
+      }
+      if (X != other.X) return false;
+      if (None != other.None) return false;
+      if (TestCase != other.TestCase) return false;
+      return Equals(_unknownFields, other._unknownFields);
+    }
+
+    [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
+    [global::System.CodeDom.Compiler.GeneratedCode("protoc", null)]
+    public override int GetHashCode() {
+      int hash = 1;
+      if (testCase_ == TestOneofCase.X) hash ^= X.GetHashCode();
+      if (testCase_ == TestOneofCase.None_) hash ^= None.GetHashCode();
+      hash ^= (int) testCase_;
+      if (_unknownFields != null) {
+        hash ^= _unknownFields.GetHashCode();
+      }
+      return hash;
+    }
+
+    [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
+    [global::System.CodeDom.Compiler.GeneratedCode("protoc", null)]
+    public override string ToString() {
+      return pb::JsonFormatter.ToDiagnosticString(this);
+    }
+
+    [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
+    [global::System.CodeDom.Compiler.GeneratedCode("protoc", null)]
+    public void WriteTo(pb::CodedOutputStream output) {
+    #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
+      output.WriteRawMessage(this);
+    #else
+      if (testCase_ == TestOneofCase.X) {
+        output.WriteRawTag(10);
+        output.WriteString(X);
+      }
+      if (testCase_ == TestOneofCase.None_) {
+        output.WriteRawTag(18);
+        output.WriteString(None);
+      }
+      if (_unknownFields != null) {
+        _unknownFields.WriteTo(output);
+      }
+    #endif
+    }
+
+    #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
+    [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
+    [global::System.CodeDom.Compiler.GeneratedCode("protoc", null)]
+    void pb::IBufferMessage.InternalWriteTo(ref pb::WriteContext output) {
+      if (testCase_ == TestOneofCase.X) {
+        output.WriteRawTag(10);
+        output.WriteString(X);
+      }
+      if (testCase_ == TestOneofCase.None_) {
+        output.WriteRawTag(18);
+        output.WriteString(None);
+      }
+      if (_unknownFields != null) {
+        _unknownFields.WriteTo(ref output);
+      }
+    }
+    #endif
+
+    [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
+    [global::System.CodeDom.Compiler.GeneratedCode("protoc", null)]
+    public int CalculateSize() {
+      int size = 0;
+      if (testCase_ == TestOneofCase.X) {
+        size += 1 + pb::CodedOutputStream.ComputeStringSize(X);
+      }
+      if (testCase_ == TestOneofCase.None_) {
+        size += 1 + pb::CodedOutputStream.ComputeStringSize(None);
+      }
+      if (_unknownFields != null) {
+        size += _unknownFields.CalculateSize();
+      }
+      return size;
+    }
+
+    [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
+    [global::System.CodeDom.Compiler.GeneratedCode("protoc", null)]
+    public void MergeFrom(OneofWithNoneField other) {
+      if (other == null) {
+        return;
+      }
+      switch (other.TestCase) {
+        case TestOneofCase.X:
+          X = other.X;
+          break;
+        case TestOneofCase.None_:
+          None = other.None;
+          break;
+      }
+
+      _unknownFields = pb::UnknownFieldSet.MergeFrom(_unknownFields, other._unknownFields);
+    }
+
+    [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
+    [global::System.CodeDom.Compiler.GeneratedCode("protoc", null)]
+    public void MergeFrom(pb::CodedInputStream input) {
+    #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
+      input.ReadRawMessage(this);
+    #else
+      uint tag;
+      while ((tag = input.ReadTag()) != 0) {
+        switch(tag) {
+          default:
+            _unknownFields = pb::UnknownFieldSet.MergeFieldFrom(_unknownFields, input);
+            break;
+          case 10: {
+            X = input.ReadString();
+            break;
+          }
+          case 18: {
+            None = input.ReadString();
+            break;
+          }
+        }
+      }
+    #endif
+    }
+
+    #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
+    [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
+    [global::System.CodeDom.Compiler.GeneratedCode("protoc", null)]
+    void pb::IBufferMessage.InternalMergeFrom(ref pb::ParseContext input) {
+      uint tag;
+      while ((tag = input.ReadTag()) != 0) {
+        switch(tag) {
+          default:
+            _unknownFields = pb::UnknownFieldSet.MergeFieldFrom(_unknownFields, ref input);
+            break;
+          case 10: {
+            X = input.ReadString();
+            break;
+          }
+          case 18: {
+            None = input.ReadString();
+            break;
+          }
+        }
+      }
+    }
+    #endif
+
+  }
+
+  public sealed partial class OneofWithNoneName : pb::IMessage<OneofWithNoneName>
+  #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
+      , pb::IBufferMessage
+  #endif
+  {
+    private static readonly pb::MessageParser<OneofWithNoneName> _parser = new pb::MessageParser<OneofWithNoneName>(() => new OneofWithNoneName());
+    private pb::UnknownFieldSet _unknownFields;
+    [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
+    [global::System.CodeDom.Compiler.GeneratedCode("protoc", null)]
+    public static pb::MessageParser<OneofWithNoneName> Parser { get { return _parser; } }
+
+    [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
+    [global::System.CodeDom.Compiler.GeneratedCode("protoc", null)]
+    public static pbr::MessageDescriptor Descriptor {
+      get { return global::UnitTest.Issues.TestProtos.UnittestIssuesReflection.Descriptor.MessageTypes[13]; }
+    }
+
+    [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
+    [global::System.CodeDom.Compiler.GeneratedCode("protoc", null)]
+    pbr::MessageDescriptor pb::IMessage.Descriptor {
+      get { return Descriptor; }
+    }
+
+    [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
+    [global::System.CodeDom.Compiler.GeneratedCode("protoc", null)]
+    public OneofWithNoneName() {
+      OnConstruction();
+    }
+
+    partial void OnConstruction();
+
+    [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
+    [global::System.CodeDom.Compiler.GeneratedCode("protoc", null)]
+    public OneofWithNoneName(OneofWithNoneName other) : this() {
+      switch (other.NoneCase) {
+        case NoneOneofCase.X:
+          X = other.X;
+          break;
+        case NoneOneofCase.Y:
+          Y = other.Y;
+          break;
+      }
+
+      _unknownFields = pb::UnknownFieldSet.Clone(other._unknownFields);
+    }
+
+    [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
+    [global::System.CodeDom.Compiler.GeneratedCode("protoc", null)]
+    public OneofWithNoneName Clone() {
+      return new OneofWithNoneName(this);
+    }
+
+    /// <summary>Field number for the "x" field.</summary>
+    public const int XFieldNumber = 1;
+    [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
+    [global::System.CodeDom.Compiler.GeneratedCode("protoc", null)]
+    public string X {
+      get { return noneCase_ == NoneOneofCase.X ? (string) none_ : ""; }
+      set {
+        none_ = pb::ProtoPreconditions.CheckNotNull(value, "value");
+        noneCase_ = NoneOneofCase.X;
+      }
+    }
+
+    /// <summary>Field number for the "y" field.</summary>
+    public const int YFieldNumber = 2;
+    [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
+    [global::System.CodeDom.Compiler.GeneratedCode("protoc", null)]
+    public string Y {
+      get { return noneCase_ == NoneOneofCase.Y ? (string) none_ : ""; }
+      set {
+        none_ = pb::ProtoPreconditions.CheckNotNull(value, "value");
+        noneCase_ = NoneOneofCase.Y;
+      }
+    }
+
+    private object none_;
+    /// <summary>Enum of possible cases for the "none" oneof.</summary>
+    public enum NoneOneofCase {
+      None = 0,
+      X = 1,
+      Y = 2,
+    }
+    private NoneOneofCase noneCase_ = NoneOneofCase.None;
+    [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
+    [global::System.CodeDom.Compiler.GeneratedCode("protoc", null)]
+    public NoneOneofCase NoneCase {
+      get { return noneCase_; }
+    }
+
+    [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
+    [global::System.CodeDom.Compiler.GeneratedCode("protoc", null)]
+    public void ClearNone() {
+      noneCase_ = NoneOneofCase.None;
+      none_ = null;
+    }
+
+    [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
+    [global::System.CodeDom.Compiler.GeneratedCode("protoc", null)]
+    public override bool Equals(object other) {
+      return Equals(other as OneofWithNoneName);
+    }
+
+    [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
+    [global::System.CodeDom.Compiler.GeneratedCode("protoc", null)]
+    public bool Equals(OneofWithNoneName other) {
+      if (ReferenceEquals(other, null)) {
+        return false;
+      }
+      if (ReferenceEquals(other, this)) {
+        return true;
+      }
+      if (X != other.X) return false;
+      if (Y != other.Y) return false;
+      if (NoneCase != other.NoneCase) return false;
+      return Equals(_unknownFields, other._unknownFields);
+    }
+
+    [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
+    [global::System.CodeDom.Compiler.GeneratedCode("protoc", null)]
+    public override int GetHashCode() {
+      int hash = 1;
+      if (noneCase_ == NoneOneofCase.X) hash ^= X.GetHashCode();
+      if (noneCase_ == NoneOneofCase.Y) hash ^= Y.GetHashCode();
+      hash ^= (int) noneCase_;
+      if (_unknownFields != null) {
+        hash ^= _unknownFields.GetHashCode();
+      }
+      return hash;
+    }
+
+    [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
+    [global::System.CodeDom.Compiler.GeneratedCode("protoc", null)]
+    public override string ToString() {
+      return pb::JsonFormatter.ToDiagnosticString(this);
+    }
+
+    [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
+    [global::System.CodeDom.Compiler.GeneratedCode("protoc", null)]
+    public void WriteTo(pb::CodedOutputStream output) {
+    #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
+      output.WriteRawMessage(this);
+    #else
+      if (noneCase_ == NoneOneofCase.X) {
+        output.WriteRawTag(10);
+        output.WriteString(X);
+      }
+      if (noneCase_ == NoneOneofCase.Y) {
+        output.WriteRawTag(18);
+        output.WriteString(Y);
+      }
+      if (_unknownFields != null) {
+        _unknownFields.WriteTo(output);
+      }
+    #endif
+    }
+
+    #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
+    [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
+    [global::System.CodeDom.Compiler.GeneratedCode("protoc", null)]
+    void pb::IBufferMessage.InternalWriteTo(ref pb::WriteContext output) {
+      if (noneCase_ == NoneOneofCase.X) {
+        output.WriteRawTag(10);
+        output.WriteString(X);
+      }
+      if (noneCase_ == NoneOneofCase.Y) {
+        output.WriteRawTag(18);
+        output.WriteString(Y);
+      }
+      if (_unknownFields != null) {
+        _unknownFields.WriteTo(ref output);
+      }
+    }
+    #endif
+
+    [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
+    [global::System.CodeDom.Compiler.GeneratedCode("protoc", null)]
+    public int CalculateSize() {
+      int size = 0;
+      if (noneCase_ == NoneOneofCase.X) {
+        size += 1 + pb::CodedOutputStream.ComputeStringSize(X);
+      }
+      if (noneCase_ == NoneOneofCase.Y) {
+        size += 1 + pb::CodedOutputStream.ComputeStringSize(Y);
+      }
+      if (_unknownFields != null) {
+        size += _unknownFields.CalculateSize();
+      }
+      return size;
+    }
+
+    [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
+    [global::System.CodeDom.Compiler.GeneratedCode("protoc", null)]
+    public void MergeFrom(OneofWithNoneName other) {
+      if (other == null) {
+        return;
+      }
+      switch (other.NoneCase) {
+        case NoneOneofCase.X:
+          X = other.X;
+          break;
+        case NoneOneofCase.Y:
+          Y = other.Y;
+          break;
+      }
+
+      _unknownFields = pb::UnknownFieldSet.MergeFrom(_unknownFields, other._unknownFields);
+    }
+
+    [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
+    [global::System.CodeDom.Compiler.GeneratedCode("protoc", null)]
+    public void MergeFrom(pb::CodedInputStream input) {
+    #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
+      input.ReadRawMessage(this);
+    #else
+      uint tag;
+      while ((tag = input.ReadTag()) != 0) {
+        switch(tag) {
+          default:
+            _unknownFields = pb::UnknownFieldSet.MergeFieldFrom(_unknownFields, input);
+            break;
+          case 10: {
+            X = input.ReadString();
+            break;
+          }
+          case 18: {
+            Y = input.ReadString();
+            break;
+          }
+        }
+      }
+    #endif
+    }
+
+    #if !GOOGLE_PROTOBUF_REFSTRUCT_COMPATIBILITY_MODE
+    [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
+    [global::System.CodeDom.Compiler.GeneratedCode("protoc", null)]
+    void pb::IBufferMessage.InternalMergeFrom(ref pb::ParseContext input) {
+      uint tag;
+      while ((tag = input.ReadTag()) != 0) {
+        switch(tag) {
+          default:
+            _unknownFields = pb::UnknownFieldSet.MergeFieldFrom(_unknownFields, ref input);
+            break;
+          case 10: {
+            X = input.ReadString();
+            break;
+          }
+          case 18: {
+            Y = input.ReadString();
+            break;
+          }
+        }
+      }
+    }
+    #endif
+
+  }
+
   #endregion
 
 }
diff --git a/csharp/src/Google.Protobuf.Test/testprotos.pb b/csharp/src/Google.Protobuf.Test/testprotos.pb
index 50fd48c526..b1dfc97ea7 100644
Binary files a/csharp/src/Google.Protobuf.Test/testprotos.pb and b/csharp/src/Google.Protobuf.Test/testprotos.pb differ