diff --git a/src/StripeTests/Infrastructure/JsonConverters/STJAnyOfConverterTest.cs b/src/StripeTests/Infrastructure/JsonConverters/STJAnyOfConverterTest.cs
new file mode 100644
index 0000000000..9f7c6ff5c0
--- /dev/null
+++ b/src/StripeTests/Infrastructure/JsonConverters/STJAnyOfConverterTest.cs
@@ -0,0 +1,113 @@
+namespace StripeTests
+{
+    using System.Text.Json;
+    using System.Text.Json.Serialization;
+    using Stripe;
+    using Stripe.Infrastructure;
+    using Xunit;
+
+    public class STJAnyOfConverterTest : BaseStripeTest
+    {
+        [Fact]
+        public void DeserializeFirstType()
+        {
+            var json = "{\n  \"any_of\": \"String!\"\n}";
+            var obj = JsonSerializer.Deserialize<TestObject>(json);
+
+            Assert.NotNull(obj.AnyOf);
+            Assert.Equal("String!", obj.AnyOf);
+        }
+
+        [Fact]
+        public void DeserializeSecondType()
+        {
+            var json = "{\n  \"any_of\": {\n    \"id\": \"id_123\",\n    \"bar\": 42\n  }\n}";
+            var obj = JsonSerializer.Deserialize<TestObject>(json);
+
+            Assert.NotNull(obj.AnyOf);
+            Assert.Equal("id_123", ((TestSubObject)obj.AnyOf).Id);
+            Assert.Equal(42, ((TestSubObject)obj.AnyOf).Bar);
+        }
+
+        [Fact]
+        public void DeserializeNull()
+        {
+            var json = "{\n  \"any_of\": null\n}";
+            var obj = JsonSerializer.Deserialize<TestObject>(json);
+
+            Assert.Null(obj.AnyOf);
+        }
+
+        [Fact]
+        public void DeserializeUnexpectedType()
+        {
+            var json = "{\n  \"any_of\": []\n}";
+
+            var exception = Assert.Throws<JsonException>(() =>
+                JsonSerializer.Deserialize<TestObject>(json));
+
+            Assert.Contains(
+                "Cannot deserialize the current JSON object into any of the expected types",
+                exception.Message);
+        }
+
+        [Fact]
+        public void SerializeFirstType()
+        {
+            var obj = new TestObject
+            {
+                AnyOf = "String!",
+            };
+
+            var expected = "{\n  \"any_of\": \"String!\"\n}";
+            Assert.Equal(expected, obj.ToJson().Replace("\r\n", "\n"));
+        }
+
+        [Fact]
+        public void SerializeSecondType()
+        {
+            var obj = new TestObject
+            {
+                AnyOf = new TestSubObject
+                {
+                    Id = "id_123",
+                    Bar = 42,
+                },
+            };
+
+            var expected =
+                "{\n  \"any_of\": {\n    \"id\": \"id_123\",\n    \"bar\": 42\n  }\n}";
+            Assert.Equal(expected, obj.ToJson().Replace("\r\n", "\n"));
+        }
+
+        [Fact]
+        public void SerializeNull()
+        {
+            var obj = new TestObject
+            {
+                AnyOf = null,
+            };
+
+            var expected = "{\n  \"any_of\": null\n}";
+            Assert.Equal(expected, obj.ToJson().Replace("\r\n", "\n"));
+        }
+
+        [JsonConverter(typeof(STJStripeEntityConverter))]
+        private class TestSubObject : StripeEntity<TestSubObject>, IHasId
+        {
+            [JsonPropertyName("id")]
+            public string Id { get; set; }
+
+            [JsonPropertyName("bar")]
+            public int Bar { get; set; }
+        }
+
+        [JsonConverter(typeof(STJStripeEntityConverter))]
+        private class TestObject : StripeEntity<TestObject>
+        {
+            [JsonPropertyName("any_of")]
+            [JsonConverter(typeof(STJAnyOfConverter))]
+            internal AnyOf<string, TestSubObject> AnyOf { get; set; }
+        }
+    }
+}
diff --git a/src/StripeTests/Infrastructure/JsonConverters/STJExpandableFieldConverterTest.cs b/src/StripeTests/Infrastructure/JsonConverters/STJExpandableFieldConverterTest.cs
new file mode 100644
index 0000000000..946fa0d900
--- /dev/null
+++ b/src/StripeTests/Infrastructure/JsonConverters/STJExpandableFieldConverterTest.cs
@@ -0,0 +1,195 @@
+namespace StripeTests
+{
+    using System.Collections.Generic;
+    using System.IO;
+    using System.Linq;
+    using System.Text.Json;
+    using System.Text.Json.Serialization;
+    using Stripe;
+    using Stripe.Infrastructure;
+    using Xunit;
+
+    public class STJExpandableFieldConverterTest : BaseStripeTest
+    {
+        [Fact]
+        public void DeserializeNotExpanded()
+        {
+            var json = "{\n  \"nested\": \"id_not_expanded\"\n}";
+            var obj = JsonSerializer.Deserialize<TestTopLevelObject>(json);
+
+            Assert.Equal("id_not_expanded", obj.NestedId);
+            Assert.Null(obj.Nested);
+        }
+
+        [Fact]
+        public void DeserializeExpanded()
+        {
+            var json = "{\n  \"nested\": {\n    \"id\": \"id_expanded\",\n    \"bar\": 42\n  }\n}";
+            var obj = JsonSerializer.Deserialize<TestTopLevelObject>(json);
+
+            Assert.Equal("id_expanded", obj.NestedId);
+            Assert.NotNull(obj.Nested);
+            Assert.Equal("id_expanded", obj.Nested.Id);
+            Assert.Equal(42, obj.Nested.Bar);
+        }
+
+        [Fact]
+        public void DeserializeNull()
+        {
+            var json = "{\n  \"nested\": null\n}";
+            var obj = JsonSerializer.Deserialize<TestTopLevelObject>(json);
+
+            Assert.Null(obj.NestedId);
+            Assert.Null(obj.Nested);
+        }
+
+        [Fact]
+        public void SerializeNotExpanded()
+        {
+            var obj = new TestTopLevelObject
+            {
+                InternalNested = new ExpandableField<TestNestedObject>
+                {
+                    Id = "id_not_expanded",
+                    ExpandedObject = null,
+                },
+            };
+
+            var expected = "{\"nested\":\"id_not_expanded\"}";
+            var actual = JsonSerializer.Serialize(obj);
+            Assert.Equal(expected, actual);
+
+            var indentedExpected = "{\n  \"nested\": \"id_not_expanded\"\n}";
+            var options = new JsonSerializerOptions { WriteIndented = true };
+            var indentedActual = JsonSerializer.Serialize(obj, options);
+            Assert.Equal(indentedExpected, indentedActual);
+        }
+
+        [Fact]
+        public void SerializeExpanded()
+        {
+            var nested = new TestNestedObject
+            {
+                Id = "id_expanded",
+                Bar = 42,
+            };
+            var obj = new TestTopLevelObject
+            {
+                InternalNested = new ExpandableField<TestNestedObject>
+                {
+                    Id = nested.Id,
+                    ExpandedObject = nested,
+                },
+            };
+
+            var expected =
+                "{\"nested\":{\"id\":\"id_expanded\",\"bar\":42}}";
+            var actual = JsonSerializer.Serialize(obj);
+            Assert.Equal(expected, actual);
+
+            var indentedExpected =
+                "{\n  \"nested\": {\n    \"id\": \"id_expanded\",\n    \"bar\": 42\n  }\n}";
+            var options = new JsonSerializerOptions { WriteIndented = true };
+            var indentedActual = JsonSerializer.Serialize(obj, options);
+            Assert.Equal(indentedExpected, indentedActual);
+        }
+
+        [Fact]
+        public void SerializeListOfExpanded()
+        {
+            var nested = new TestNestedObject
+            {
+                Id = "id_expanded",
+                Bar = 42,
+            };
+            var obj = new TestTopLevelObjectWithList
+            {
+                InternalNestedList = new List<ExpandableField<TestNestedObject>>()
+                {
+                    new ExpandableField<TestNestedObject>
+                    {
+                        Id = nested.Id,
+                        ExpandedObject = nested,
+                    },
+                },
+            };
+
+            var expected =
+                "{\"nested_list\":[{\"id\":\"id_expanded\",\"bar\":42}]}";
+            var actual = JsonSerializer.Serialize(obj);
+            Assert.Equal(expected, actual);
+
+            var indentedExpected =
+                "{\n  \"nested_list\": [\n    {\n      \"id\": \"id_expanded\",\n      \"bar\": 42\n    }\n  ]\n}";
+            var options = new JsonSerializerOptions { WriteIndented = true };
+            var indentedActual = JsonSerializer.Serialize(obj, options);
+            Assert.Equal(indentedExpected, indentedActual);
+        }
+
+        [Fact]
+        public void SerializeNull()
+        {
+            var obj = new TestTopLevelObject
+            {
+                InternalNested = new ExpandableField<TestNestedObject>
+                {
+                    Id = null,
+                    ExpandedObject = null,
+                },
+            };
+
+            var expected = "{\"nested\":null}";
+            var actual = JsonSerializer.Serialize(obj);
+            Assert.Equal(expected, actual);
+
+            var indentedExpected = "{\n  \"nested\": null\n}";
+            var options = new JsonSerializerOptions { WriteIndented = true };
+            var indentedActual = JsonSerializer.Serialize(obj, options);
+            Assert.Equal(indentedExpected, indentedActual);
+        }
+
+        private class TestNestedObject : StripeEntity<TestNestedObject>, IHasId
+        {
+            [JsonPropertyName("id")]
+            public string Id { get; set; }
+
+            [JsonPropertyName("bar")]
+            public int Bar { get; set; }
+        }
+
+        [JsonConverter(typeof(STJStripeEntityConverter))]
+        private class TestTopLevelObject : StripeEntity<TestTopLevelObject>
+        {
+            [JsonIgnore]
+            public string NestedId => this.InternalNested.Id;
+
+            [JsonIgnore]
+            public TestNestedObject Nested => this.InternalNested.ExpandedObject;
+
+            [JsonPropertyName("nested")]
+            [JsonConverter(typeof(STJExpandableFieldConverter<TestNestedObject>))]
+            internal ExpandableField<TestNestedObject> InternalNested { get; set; }
+        }
+
+        [JsonConverter(typeof(STJStripeEntityConverter))]
+        private class TestTopLevelObjectWithList : StripeEntity<TestTopLevelObjectWithList>
+        {
+            [JsonIgnore]
+            public List<string> NestedListIds
+            {
+                get => this.InternalNestedList?.Select((x) => x.Id).ToList();
+                set => this.InternalNestedList = SetExpandableArrayIds<TestNestedObject>(value);
+            }
+
+            [JsonIgnore]
+            public List<TestNestedObject> NestedList
+            {
+                get => this.InternalNestedList?.Select((x) => x.ExpandedObject).ToList();
+                set => this.InternalNestedList = SetExpandableArrayObjects(value);
+            }
+
+            [JsonPropertyName("nested_list")]
+            internal List<ExpandableField<TestNestedObject>> InternalNestedList { get; set; }
+        }
+    }
+}
diff --git a/src/StripeTests/Wholesome/CorrectJsonConvertersForTypes.cs b/src/StripeTests/Wholesome/CorrectJsonConvertersForTypes.cs
index 6bfdde9f64..12eaa382b1 100644
--- a/src/StripeTests/Wholesome/CorrectJsonConvertersForTypes.cs
+++ b/src/StripeTests/Wholesome/CorrectJsonConvertersForTypes.cs
@@ -103,6 +103,13 @@ public void Check()
                         continue;
                     }
 
+                    // if we have a Int64StringConverter on a long type, assume its good.
+                    if ((property.PropertyType == typeof(long) || property.PropertyType == typeof(long?))
+                         && actualConverterName == "Int64StringConverter")
+                    {
+                        continue;
+                    }
+
                     results.Add(
                         $"{stripeClass.Name}.{property.Name}, expected = {expectedConverterName}, "
                             + $"actual = {actualConverterName}");
diff --git a/src/StripeTests/Wholesome/PropertiesHaveAllNecessaryJsonAttributes.cs b/src/StripeTests/Wholesome/PropertiesHaveAllNecessaryJsonAttributes.cs
index 5047ab7794..6b2132372d 100644
--- a/src/StripeTests/Wholesome/PropertiesHaveAllNecessaryJsonAttributes.cs
+++ b/src/StripeTests/Wholesome/PropertiesHaveAllNecessaryJsonAttributes.cs
@@ -55,6 +55,24 @@ public void Check()
                         }
                     }
 
+                    if (property.PropertyType == typeof(long) || property.PropertyType == typeof(long?))
+                    {
+                        var jsonAttribute = property.GetCustomAttribute(typeof(Newtonsoft.Json.JsonConverterAttribute), false) as Newtonsoft.Json.JsonConverterAttribute;
+                        var stjAttribute = property.GetCustomAttribute(typeof(JsonNumberHandlingAttribute)) as JsonNumberHandlingAttribute;
+                        if (jsonAttribute?.ConverterType == typeof(Int64StringConverter))
+                        {
+                            var hasCorrectAttributes =
+                                (stjAttribute.Handling & (JsonNumberHandling.AllowReadingFromString | JsonNumberHandling.WriteAsString)) != 0;
+
+                            if (!hasCorrectAttributes)
+                            {
+                                results.Add($"{type.FullName}.{property.Name}");
+                            }
+
+                            continue;
+                        }
+                    }
+
                     foreach (Attribute attribute in property.GetCustomAttributes())
                     {
                         if (attribute.GetType().Namespace.StartsWith("Newtonsoft", true, null))