diff --git a/LanguageExt.CodeGen/CodeGenUtil.cs b/LanguageExt.CodeGen/CodeGenUtil.cs
index 8de67c3a9..71b0ea1a5 100644
--- a/LanguageExt.CodeGen/CodeGenUtil.cs
+++ b/LanguageExt.CodeGen/CodeGenUtil.cs
@@ -1980,7 +1980,7 @@ static MemberDeclarationSyntax[] MakeSerialisationMembers(string typeName, List<
                             Identifier(typeName))
                         .WithModifiers(
                             TokenList(
-                                Token(SyntaxKind.ProtectedKeyword)))
+                                Token(SyntaxKind.PrivateKeyword)))
                         .WithParameterList(
                             ParameterList(
                                 SeparatedList<ParameterSyntax>(
@@ -2213,9 +2213,7 @@ public static TypeDeclarationSyntax MakeCaseType(
                                     Token(SyntaxKind.CommaToken),
                                     SimpleBaseType(thisComparableType),
                                     Token(SyntaxKind.CommaToken),
-                                    SimpleBaseType(comparableType),
-                                    Token(SyntaxKind.CommaToken),
-                                    SimpleBaseType(serializableType)
+                                    SimpleBaseType(comparableType)
                                 }))),
                 BaseSpec.Abstract =>
                     type.WithBaseList(
@@ -2228,9 +2226,7 @@ public static TypeDeclarationSyntax MakeCaseType(
                                     Token(SyntaxKind.CommaToken),
                                     SimpleBaseType(thisComparableType),
                                     Token(SyntaxKind.CommaToken),
-                                    SimpleBaseType(comparableType),
-                                    Token(SyntaxKind.CommaToken),
-                                    SimpleBaseType(serializableType)
+                                    SimpleBaseType(comparableType)
                                 }))),
                 _ =>
                     type.WithBaseList(
@@ -2241,9 +2237,7 @@ public static TypeDeclarationSyntax MakeCaseType(
                                     Token(SyntaxKind.CommaToken),
                                     SimpleBaseType(thisComparableType),
                                     Token(SyntaxKind.CommaToken),
-                                    SimpleBaseType(comparableType),
-                                    Token(SyntaxKind.CommaToken),
-                                    SimpleBaseType(serializableType)
+                                    SimpleBaseType(comparableType)
                                 })))
             };
 
diff --git a/LanguageExt.Tests/UnionCustomJsonSerializerTests.cs b/LanguageExt.Tests/UnionCustomJsonSerializerTests.cs
new file mode 100644
index 000000000..fddcf6a1d
--- /dev/null
+++ b/LanguageExt.Tests/UnionCustomJsonSerializerTests.cs
@@ -0,0 +1,107 @@
+using System;
+using System.Linq;
+using System.Reflection;
+using Newtonsoft.Json;
+using Newtonsoft.Json.Linq;
+using Xunit;
+
+namespace LanguageExt.Tests
+{
+    public partial class UnionCustomJsonSerializerTests
+    {
+        [Union]
+        [MyUnion]
+        abstract partial class UnionTestClass
+        {
+            public abstract UnionTestClass A();
+            public abstract UnionTestClass B(int i);
+            public abstract UnionTestClass C(int i);
+            public abstract UnionTestClass D(int i, int j);
+        }
+        
+        [AttributeUsage(AttributeTargets.Class, Inherited = false)]
+        public class MyUnionAttribute : Attribute
+        {
+        }
+        
+        public class UnionJsonReadConverter : JsonConverter
+        {
+            public override void WriteJson(JsonWriter writer, object value, JsonSerializer serializer) => throw new NotImplementedException();
+
+            public override object ReadJson(JsonReader reader, Type objectType, object existingValue, JsonSerializer serializer)
+            {
+                string typeName = null;
+                JObject typeValueToken = null;
+                if (reader.TokenType != JsonToken.StartObject) throw new Exception();
+                while (reader.Read())
+                {
+                    if (reader.TokenType == JsonToken.EndObject) break;
+                    if (reader.TokenType != JsonToken.PropertyName) throw new Exception();
+                    if ((string) reader.Value == "Type")
+                    {
+                        if (!reader.Read()) throw new Exception();
+                        if (typeName != null) throw new Exception();
+                        if (reader.TokenType != JsonToken.String) throw new Exception();
+                        typeName = (string) reader.Value;
+                    }
+                    else if ((string) reader.Value == "Value")
+                    {
+                        if (typeValueToken != null) throw new Exception();
+                        if (!reader.Read()) throw new Exception();
+                        if (reader.TokenType != JsonToken.StartObject) throw new Exception();
+                        typeValueToken = JObject.Load(reader);
+                    }
+                }
+
+                var type = objectType.Assembly.GetTypes().Where(_ => objectType.IsAssignableFrom(_) && _.Name == typeName).Single();
+                var result = typeValueToken.ToObject(type, serializer);
+                return result;
+            }
+
+            public override bool CanWrite => false;
+            public override bool CanConvert(Type objectType) => objectType.IsClass && objectType.GetCustomAttribute<MyUnionAttribute>() != null;
+        }
+         
+        public class UnionJsonWriteConverter : JsonConverter
+        {
+            public override void WriteJson(JsonWriter writer, object value, JsonSerializer serializer)
+            {
+                var t = value.GetType();
+                writer.WriteStartObject();
+                writer.WritePropertyName("Type");
+                writer.WriteValue(t.Name);
+                writer.WritePropertyName("Value");
+                writer.WriteStartObject();
+                foreach (var fieldInfo in t.GetFields(BindingFlags.Instance | BindingFlags.Public))
+                {
+                    writer.WritePropertyName(fieldInfo.Name);
+                    serializer.Serialize(writer, fieldInfo.GetValue(value));
+                }
+                writer.WriteEndObject();
+                writer.WriteEndObject();
+            }
+
+            public override object ReadJson(JsonReader reader, Type objectType, object existingValue, JsonSerializer serializer) =>
+                new NotImplementedException();
+
+            public override bool CanRead => false;
+
+            public override bool CanConvert(Type objectType) => objectType.IsClass && objectType.BaseType?.BaseType?.GetCustomAttribute<MyUnionAttribute>() != null;
+        }
+        
+        [Fact]
+        public void UnionFromJson()
+        {
+            var json = @"{""Type"":""B"",""Value"":{""I"":42}}";
+            var x = JsonConvert.DeserializeObject<UnionTestClass>(json, new UnionJsonReadConverter()) as B;
+            Assert.Equal(42, x?.I);
+        }
+        
+        [Fact]
+        public void UnionToJson()
+        {
+            var x = JsonConvert.SerializeObject(UnionTestClassCon.B(42), new UnionJsonWriteConverter());
+            Assert.Equal(@"{""Type"":""B"",""Value"":{""I"":42}}", x);
+        }
+    }
+}
diff --git a/LanguageExt.Tests/UnionJsonSerializerTests.cs b/LanguageExt.Tests/UnionJsonSerializerTests.cs
new file mode 100644
index 000000000..2582e6af0
--- /dev/null
+++ b/LanguageExt.Tests/UnionJsonSerializerTests.cs
@@ -0,0 +1,40 @@
+using System.Runtime.Serialization;
+using Newtonsoft.Json;
+using Xunit;
+
+namespace LanguageExt.Tests
+{
+    public partial class UnionJsonSerializerTests
+    { 
+        [Union]
+        public abstract partial class LightControl
+        {
+            public abstract LightControl OnOff(bool enabled);
+            public abstract LightControl Dimmer(int value);
+        }
+
+        [Fact]
+        public void UnionInstanceFromJson()
+        {
+            var json = @"{""Value"":100}";
+            var x = JsonConvert.DeserializeObject<Dimmer>(json);
+            Assert.Equal(100, x.Value);
+        }
+        
+        [Fact]
+        public void UnionInstanceToJson()
+        {
+            Assert.Equal(@"{""Value"":100}", JsonConvert.SerializeObject(LightControlCon.Dimmer(100)));
+        }        
+        
+        [Fact]
+        public void UnionRoundTrip()
+        {
+            Assert.Equal(LightControlCon.OnOff(true), JsonConvert.DeserializeObject<OnOff>(JsonConvert.SerializeObject(LightControlCon.OnOff(true))));
+            Assert.Equal(LightControlCon.OnOff(false), JsonConvert.DeserializeObject<OnOff>(JsonConvert.SerializeObject(LightControlCon.OnOff(false))));
+            Assert.Equal(LightControlCon.Dimmer(10), JsonConvert.DeserializeObject<Dimmer>(JsonConvert.SerializeObject(LightControlCon.Dimmer(10))));
+            Assert.Equal(LightControlCon.Dimmer(90), JsonConvert.DeserializeObject<Dimmer>(JsonConvert.SerializeObject(LightControlCon.Dimmer(90))));
+            
+        }
+    }
+}
diff --git a/LanguageExt.Tests/UnionTests.cs b/LanguageExt.Tests/UnionTests.cs
deleted file mode 100644
index 94817ac1f..000000000
--- a/LanguageExt.Tests/UnionTests.cs
+++ /dev/null
@@ -1,23 +0,0 @@
-using Newtonsoft.Json;
-using Xunit;
-
-namespace LanguageExt.Tests
-{
-    public partial class UnionTests
-    {
-        [Union]
-        public abstract partial class LightControl
-        {
-            public abstract LightControl OnOff(bool enabled);
-            public abstract LightControl Dimmer(int value);
-        }
-
-        [Fact]
-        public void FromJson()
-        {
-            var json = @"{""Value"": 100}";
-            var x = JsonConvert.DeserializeObject<Dimmer>(json);
-            Assert.Equal(100, x.Value);
-        }
-    }
-}