diff --git a/src/Json.Schema.ToDotNet.UnitTests/DataModelGeneratorTests.cs b/src/Json.Schema.ToDotNet.UnitTests/DataModelGeneratorTests.cs
index c21d728..3b3b50f 100644
--- a/src/Json.Schema.ToDotNet.UnitTests/DataModelGeneratorTests.cs
+++ b/src/Json.Schema.ToDotNet.UnitTests/DataModelGeneratorTests.cs
@@ -141,7 +141,7 @@ public partial class C
         [DataMember(Name = ""booleanProperty"", IsRequired = false, EmitDefaultValue = false)]
         public bool BooleanProperty { get; set; }
         [DataMember(Name = ""integerProperty"", IsRequired = false, EmitDefaultValue = false)]
-        public int IntegerProperty { get; set; }
+        public int? IntegerProperty { get; set; }
     }
 }";
 
@@ -212,7 +212,10 @@ public int GetHashCode(C obj)
 
                 result = (result * 31) + obj.NumberProperty.GetHashCode();
                 result = (result * 31) + obj.BooleanProperty.GetHashCode();
-                result = (result * 31) + obj.IntegerProperty.GetHashCode();
+                if (obj.IntegerProperty != null)
+                {
+                    result = (result * 31) + obj.IntegerProperty.GetHashCode();
+                }
             }
 
             return result;
@@ -310,29 +313,29 @@ namespace N
     public partial class C
     {
         [DataMember(Name = ""integerProperty_default"", IsRequired = false, EmitDefaultValue = false)]
-        public BigInteger IntegerProperty_default { get; set; }
+        public BigInteger? IntegerProperty_default { get; set; }
         [DataMember(Name = ""integerProperty_min_0_max_na"", IsRequired = false, EmitDefaultValue = false)]
-        public BigInteger IntegerProperty_min_0_max_na { get; set; }
+        public BigInteger? IntegerProperty_min_0_max_na { get; set; }
         [DataMember(Name = ""integerProperty_min_minus1_max_na"", IsRequired = false, EmitDefaultValue = false)]
-        public BigInteger IntegerProperty_min_minus1_max_na { get; set; }
+        public BigInteger? IntegerProperty_min_minus1_max_na { get; set; }
         [DataMember(Name = ""integerProperty_min_1_max_na"", IsRequired = false, EmitDefaultValue = false)]
-        public BigInteger IntegerProperty_min_1_max_na { get; set; }
+        public BigInteger? IntegerProperty_min_1_max_na { get; set; }
         [DataMember(Name = ""integerProperty_min_na_max_0"", IsRequired = false, EmitDefaultValue = false)]
-        public BigInteger IntegerProperty_min_na_max_0 { get; set; }
+        public BigInteger? IntegerProperty_min_na_max_0 { get; set; }
         [DataMember(Name = ""integerProperty_min_0_max_int64times10"", IsRequired = false, EmitDefaultValue = false)]
         public BigInteger IntegerProperty_min_0_max_int64times10 { get; set; }
         [DataMember(Name = ""integerProperty_min_0_max_int64"", IsRequired = false, EmitDefaultValue = false)]
-        public long IntegerProperty_min_0_max_int64 { get; set; }
+        public long? IntegerProperty_min_0_max_int64 { get; set; }
         [DataMember(Name = ""integerProperty_min_0_max_int32add1"", IsRequired = false, EmitDefaultValue = false)]
-        public long IntegerProperty_min_0_max_int32add1 { get; set; }
+        public long? IntegerProperty_min_0_max_int32add1 { get; set; }
         [DataMember(Name = ""integerProperty_min_0_max_int32"", IsRequired = false, EmitDefaultValue = false)]
-        public int IntegerProperty_min_0_max_int32 { get; set; }
+        public int? IntegerProperty_min_0_max_int32 { get; set; }
         [DataMember(Name = ""integerProperty_min_int32_max_0"", IsRequired = false, EmitDefaultValue = false)]
-        public int IntegerProperty_min_int32_max_0 { get; set; }
+        public int? IntegerProperty_min_int32_max_0 { get; set; }
         [DataMember(Name = ""integerProperty_min_int32minus1_max_0"", IsRequired = false, EmitDefaultValue = false)]
-        public long IntegerProperty_min_int32minus1_max_0 { get; set; }
+        public long? IntegerProperty_min_int32minus1_max_0 { get; set; }
         [DataMember(Name = ""integerProperty_min_int64_max_0"", IsRequired = false, EmitDefaultValue = false)]
-        public long IntegerProperty_min_int64_max_0 { get; set; }
+        public long? IntegerProperty_min_int64_max_0 { get; set; }
         [DataMember(Name = ""integerProperty_min_int64times10_max_0"", IsRequired = false, EmitDefaultValue = false)]
         public BigInteger IntegerProperty_min_int64times10_max_0 { get; set; }
         [DataMember(Name = ""integerProperty_min_huge_max_0"", IsRequired = false, EmitDefaultValue = false)]
@@ -354,35 +357,35 @@ namespace N
     public partial class C
     {
         [DataMember(Name = ""integerProperty_default"", IsRequired = false, EmitDefaultValue = false)]
-        public BigInteger IntegerProperty_default { get; set; }
+        public BigInteger? IntegerProperty_default { get; set; }
         [DataMember(Name = ""integerProperty_min_0_max_na"", IsRequired = false, EmitDefaultValue = false)]
-        public BigInteger IntegerProperty_min_0_max_na { get; set; }
+        public BigInteger? IntegerProperty_min_0_max_na { get; set; }
         [DataMember(Name = ""integerProperty_min_minus1_max_na"", IsRequired = false, EmitDefaultValue = false)]
-        public BigInteger IntegerProperty_min_minus1_max_na { get; set; }
+        public BigInteger? IntegerProperty_min_minus1_max_na { get; set; }
         [DataMember(Name = ""integerProperty_min_1_max_na"", IsRequired = false, EmitDefaultValue = false)]
-        public BigInteger IntegerProperty_min_1_max_na { get; set; }
+        public BigInteger? IntegerProperty_min_1_max_na { get; set; }
         [DataMember(Name = ""integerProperty_min_na_max_0"", IsRequired = false, EmitDefaultValue = false)]
-        public BigInteger IntegerProperty_min_na_max_0 { get; set; }
+        public BigInteger? IntegerProperty_min_na_max_0 { get; set; }
         [DataMember(Name = ""integerProperty_min_0_max_int64times10"", IsRequired = false, EmitDefaultValue = false)]
-        public BigInteger IntegerProperty_min_0_max_int64times10 { get; set; }
+        public BigInteger? IntegerProperty_min_0_max_int64times10 { get; set; }
         [DataMember(Name = ""integerProperty_min_0_max_int64"", IsRequired = false, EmitDefaultValue = false)]
-        public BigInteger IntegerProperty_min_0_max_int64 { get; set; }
+        public BigInteger? IntegerProperty_min_0_max_int64 { get; set; }
         [DataMember(Name = ""integerProperty_min_0_max_int32add1"", IsRequired = false, EmitDefaultValue = false)]
-        public BigInteger IntegerProperty_min_0_max_int32add1 { get; set; }
+        public BigInteger? IntegerProperty_min_0_max_int32add1 { get; set; }
         [DataMember(Name = ""integerProperty_min_0_max_int32"", IsRequired = false, EmitDefaultValue = false)]
-        public BigInteger IntegerProperty_min_0_max_int32 { get; set; }
+        public BigInteger? IntegerProperty_min_0_max_int32 { get; set; }
         [DataMember(Name = ""integerProperty_min_int32_max_0"", IsRequired = false, EmitDefaultValue = false)]
-        public BigInteger IntegerProperty_min_int32_max_0 { get; set; }
+        public BigInteger? IntegerProperty_min_int32_max_0 { get; set; }
         [DataMember(Name = ""integerProperty_min_int32minus1_max_0"", IsRequired = false, EmitDefaultValue = false)]
-        public BigInteger IntegerProperty_min_int32minus1_max_0 { get; set; }
+        public BigInteger? IntegerProperty_min_int32minus1_max_0 { get; set; }
         [DataMember(Name = ""integerProperty_min_int64_max_0"", IsRequired = false, EmitDefaultValue = false)]
-        public BigInteger IntegerProperty_min_int64_max_0 { get; set; }
+        public BigInteger? IntegerProperty_min_int64_max_0 { get; set; }
         [DataMember(Name = ""integerProperty_min_int64times10_max_0"", IsRequired = false, EmitDefaultValue = false)]
-        public BigInteger IntegerProperty_min_int64times10_max_0 { get; set; }
+        public BigInteger? IntegerProperty_min_int64times10_max_0 { get; set; }
         [DataMember(Name = ""integerProperty_min_huge_max_0"", IsRequired = false, EmitDefaultValue = false)]
-        public BigInteger IntegerProperty_min_huge_max_0 { get; set; }
+        public BigInteger? IntegerProperty_min_huge_max_0 { get; set; }
         [DataMember(Name = ""integerProperty_min_0_max_huge"", IsRequired = false, EmitDefaultValue = false)]
-        public BigInteger IntegerProperty_min_0_max_huge { get; set; }
+        public BigInteger? IntegerProperty_min_0_max_huge { get; set; }
     }
 }";
             const string ExpectedClass_Long =
@@ -397,35 +400,35 @@ namespace N
     public partial class C
     {
         [DataMember(Name = ""integerProperty_default"", IsRequired = false, EmitDefaultValue = false)]
-        public long IntegerProperty_default { get; set; }
+        public long? IntegerProperty_default { get; set; }
         [DataMember(Name = ""integerProperty_min_0_max_na"", IsRequired = false, EmitDefaultValue = false)]
-        public long IntegerProperty_min_0_max_na { get; set; }
+        public long? IntegerProperty_min_0_max_na { get; set; }
         [DataMember(Name = ""integerProperty_min_minus1_max_na"", IsRequired = false, EmitDefaultValue = false)]
-        public long IntegerProperty_min_minus1_max_na { get; set; }
+        public long? IntegerProperty_min_minus1_max_na { get; set; }
         [DataMember(Name = ""integerProperty_min_1_max_na"", IsRequired = false, EmitDefaultValue = false)]
-        public long IntegerProperty_min_1_max_na { get; set; }
+        public long? IntegerProperty_min_1_max_na { get; set; }
         [DataMember(Name = ""integerProperty_min_na_max_0"", IsRequired = false, EmitDefaultValue = false)]
-        public long IntegerProperty_min_na_max_0 { get; set; }
+        public long? IntegerProperty_min_na_max_0 { get; set; }
         [DataMember(Name = ""integerProperty_min_0_max_int64times10"", IsRequired = false, EmitDefaultValue = false)]
-        public long IntegerProperty_min_0_max_int64times10 { get; set; }
+        public long? IntegerProperty_min_0_max_int64times10 { get; set; }
         [DataMember(Name = ""integerProperty_min_0_max_int64"", IsRequired = false, EmitDefaultValue = false)]
-        public long IntegerProperty_min_0_max_int64 { get; set; }
+        public long? IntegerProperty_min_0_max_int64 { get; set; }
         [DataMember(Name = ""integerProperty_min_0_max_int32add1"", IsRequired = false, EmitDefaultValue = false)]
-        public long IntegerProperty_min_0_max_int32add1 { get; set; }
+        public long? IntegerProperty_min_0_max_int32add1 { get; set; }
         [DataMember(Name = ""integerProperty_min_0_max_int32"", IsRequired = false, EmitDefaultValue = false)]
-        public long IntegerProperty_min_0_max_int32 { get; set; }
+        public long? IntegerProperty_min_0_max_int32 { get; set; }
         [DataMember(Name = ""integerProperty_min_int32_max_0"", IsRequired = false, EmitDefaultValue = false)]
-        public long IntegerProperty_min_int32_max_0 { get; set; }
+        public long? IntegerProperty_min_int32_max_0 { get; set; }
         [DataMember(Name = ""integerProperty_min_int32minus1_max_0"", IsRequired = false, EmitDefaultValue = false)]
-        public long IntegerProperty_min_int32minus1_max_0 { get; set; }
+        public long? IntegerProperty_min_int32minus1_max_0 { get; set; }
         [DataMember(Name = ""integerProperty_min_int64_max_0"", IsRequired = false, EmitDefaultValue = false)]
-        public long IntegerProperty_min_int64_max_0 { get; set; }
+        public long? IntegerProperty_min_int64_max_0 { get; set; }
         [DataMember(Name = ""integerProperty_min_int64times10_max_0"", IsRequired = false, EmitDefaultValue = false)]
-        public long IntegerProperty_min_int64times10_max_0 { get; set; }
+        public long? IntegerProperty_min_int64times10_max_0 { get; set; }
         [DataMember(Name = ""integerProperty_min_huge_max_0"", IsRequired = false, EmitDefaultValue = false)]
-        public long IntegerProperty_min_huge_max_0 { get; set; }
+        public long? IntegerProperty_min_huge_max_0 { get; set; }
         [DataMember(Name = ""integerProperty_min_0_max_huge"", IsRequired = false, EmitDefaultValue = false)]
-        public long IntegerProperty_min_0_max_huge { get; set; }
+        public long? IntegerProperty_min_0_max_huge { get; set; }
     }
 }";
             const string ExpectedClass_Int =
@@ -440,35 +443,35 @@ namespace N
     public partial class C
     {
         [DataMember(Name = ""integerProperty_default"", IsRequired = false, EmitDefaultValue = false)]
-        public int IntegerProperty_default { get; set; }
+        public int? IntegerProperty_default { get; set; }
         [DataMember(Name = ""integerProperty_min_0_max_na"", IsRequired = false, EmitDefaultValue = false)]
-        public int IntegerProperty_min_0_max_na { get; set; }
+        public int? IntegerProperty_min_0_max_na { get; set; }
         [DataMember(Name = ""integerProperty_min_minus1_max_na"", IsRequired = false, EmitDefaultValue = false)]
-        public int IntegerProperty_min_minus1_max_na { get; set; }
+        public int? IntegerProperty_min_minus1_max_na { get; set; }
         [DataMember(Name = ""integerProperty_min_1_max_na"", IsRequired = false, EmitDefaultValue = false)]
-        public int IntegerProperty_min_1_max_na { get; set; }
+        public int? IntegerProperty_min_1_max_na { get; set; }
         [DataMember(Name = ""integerProperty_min_na_max_0"", IsRequired = false, EmitDefaultValue = false)]
-        public int IntegerProperty_min_na_max_0 { get; set; }
+        public int? IntegerProperty_min_na_max_0 { get; set; }
         [DataMember(Name = ""integerProperty_min_0_max_int64times10"", IsRequired = false, EmitDefaultValue = false)]
-        public int IntegerProperty_min_0_max_int64times10 { get; set; }
+        public int? IntegerProperty_min_0_max_int64times10 { get; set; }
         [DataMember(Name = ""integerProperty_min_0_max_int64"", IsRequired = false, EmitDefaultValue = false)]
-        public int IntegerProperty_min_0_max_int64 { get; set; }
+        public int? IntegerProperty_min_0_max_int64 { get; set; }
         [DataMember(Name = ""integerProperty_min_0_max_int32add1"", IsRequired = false, EmitDefaultValue = false)]
-        public int IntegerProperty_min_0_max_int32add1 { get; set; }
+        public int? IntegerProperty_min_0_max_int32add1 { get; set; }
         [DataMember(Name = ""integerProperty_min_0_max_int32"", IsRequired = false, EmitDefaultValue = false)]
-        public int IntegerProperty_min_0_max_int32 { get; set; }
+        public int? IntegerProperty_min_0_max_int32 { get; set; }
         [DataMember(Name = ""integerProperty_min_int32_max_0"", IsRequired = false, EmitDefaultValue = false)]
-        public int IntegerProperty_min_int32_max_0 { get; set; }
+        public int? IntegerProperty_min_int32_max_0 { get; set; }
         [DataMember(Name = ""integerProperty_min_int32minus1_max_0"", IsRequired = false, EmitDefaultValue = false)]
-        public int IntegerProperty_min_int32minus1_max_0 { get; set; }
+        public int? IntegerProperty_min_int32minus1_max_0 { get; set; }
         [DataMember(Name = ""integerProperty_min_int64_max_0"", IsRequired = false, EmitDefaultValue = false)]
-        public int IntegerProperty_min_int64_max_0 { get; set; }
+        public int? IntegerProperty_min_int64_max_0 { get; set; }
         [DataMember(Name = ""integerProperty_min_int64times10_max_0"", IsRequired = false, EmitDefaultValue = false)]
-        public int IntegerProperty_min_int64times10_max_0 { get; set; }
+        public int? IntegerProperty_min_int64times10_max_0 { get; set; }
         [DataMember(Name = ""integerProperty_min_huge_max_0"", IsRequired = false, EmitDefaultValue = false)]
-        public int IntegerProperty_min_huge_max_0 { get; set; }
+        public int? IntegerProperty_min_huge_max_0 { get; set; }
         [DataMember(Name = ""integerProperty_min_0_max_huge"", IsRequired = false, EmitDefaultValue = false)]
-        public int IntegerProperty_min_0_max_huge { get; set; }
+        public int? IntegerProperty_min_0_max_huge { get; set; }
     }
 }";
             GeneratesPropertiesWithIntegerTypes_Helper(GenerateJsonIntegerOption.Auto, ExpectedClass_Auto);
@@ -1347,19 +1350,19 @@ public partial class Color
         /// The value of the R component.
         /// </summary>
         [DataMember(Name = ""red"", IsRequired = false, EmitDefaultValue = false)]
-        public int Red { get; set; }
+        public int? Red { get; set; }
 
         /// <summary>
         /// The value of the G component.
         /// </summary>
         [DataMember(Name = ""green"", IsRequired = false, EmitDefaultValue = false)]
-        public int Green { get; set; }
+        public int? Green { get; set; }
 
         /// <summary>
         /// The value of the B component.
         /// </summary>
         [DataMember(Name = ""blue"", IsRequired = false, EmitDefaultValue = false)]
-        public int Blue { get; set; }
+        public int? Blue { get; set; }
     }
 }";
 
@@ -1418,9 +1421,20 @@ public int GetHashCode(Color obj)
             int result = 17;
             unchecked
             {
-                result = (result * 31) + obj.Red.GetHashCode();
-                result = (result * 31) + obj.Green.GetHashCode();
-                result = (result * 31) + obj.Blue.GetHashCode();
+                if (obj.Red != null)
+                {
+                    result = (result * 31) + obj.Red.GetHashCode();
+                }
+
+                if (obj.Green != null)
+                {
+                    result = (result * 31) + obj.Green.GetHashCode();
+                }
+
+                if (obj.Blue != null)
+                {
+                    result = (result * 31) + obj.Blue.GetHashCode();
+                }
             }
 
             return result;
@@ -1758,7 +1772,7 @@ public SNodeKind SNodeKind
         /// An integer property.
         /// </summary>
         [DataMember(Name = ""integerProperty"", IsRequired = false, EmitDefaultValue = false)]
-        public int IntegerProperty { get; set; }
+        public int? IntegerProperty { get; set; }
 
         /// <summary>
         /// An integer property with a default value.
@@ -1976,7 +1990,7 @@ public C()
         /// <param name=""dictionaryWithHintedValueProp"">
         /// An initialization value for the <see cref=""P:DictionaryWithHintedValueProp"" /> property.
         /// </param>
-        public C(int integerProperty, int integerPropertyWithDefault, double numberProperty, double numberPropertyWithDefault, string stringProperty, string stringPropertyWithDefault, bool booleanProperty, bool booleanPropertyWithTrueDefault, bool booleanPropertyWithFalseDefault, Color enumeratedPropertyWithDefault, IEnumerable<double> arrayProp, Uri uriProp, DateTime dateTimeProp, D referencedTypeProp, IEnumerable<D> arrayOfRefProp, IEnumerable<IEnumerable<D>> arrayOfArrayProp, IDictionary<string, string> dictionaryProp, IDictionary<string, double> dictionaryWithPrimitiveSchemaProp, IDictionary<string, D> dictionaryWithObjectSchemaProp, IDictionary<string, IList<D>> dictionaryWithObjectArraySchemaProp, IDictionary<Uri, D> dictionaryWithUriKeyProp, IDictionary<string, V> dictionaryWithHintedValueProp)
+        public C(int? integerProperty, int integerPropertyWithDefault, double numberProperty, double numberPropertyWithDefault, string stringProperty, string stringPropertyWithDefault, bool booleanProperty, bool booleanPropertyWithTrueDefault, bool booleanPropertyWithFalseDefault, Color enumeratedPropertyWithDefault, IEnumerable<double> arrayProp, Uri uriProp, DateTime dateTimeProp, D referencedTypeProp, IEnumerable<D> arrayOfRefProp, IEnumerable<IEnumerable<D>> arrayOfArrayProp, IDictionary<string, string> dictionaryProp, IDictionary<string, double> dictionaryWithPrimitiveSchemaProp, IDictionary<string, D> dictionaryWithObjectSchemaProp, IDictionary<string, IList<D>> dictionaryWithObjectArraySchemaProp, IDictionary<Uri, D> dictionaryWithUriKeyProp, IDictionary<string, V> dictionaryWithHintedValueProp)
         {
             Init(integerProperty, integerPropertyWithDefault, numberProperty, numberPropertyWithDefault, stringProperty, stringPropertyWithDefault, booleanProperty, booleanPropertyWithTrueDefault, booleanPropertyWithFalseDefault, enumeratedPropertyWithDefault, arrayProp, uriProp, dateTimeProp, referencedTypeProp, arrayOfRefProp, arrayOfArrayProp, dictionaryProp, dictionaryWithPrimitiveSchemaProp, dictionaryWithObjectSchemaProp, dictionaryWithObjectArraySchemaProp, dictionaryWithUriKeyProp, dictionaryWithHintedValueProp);
         }
@@ -2018,7 +2032,7 @@ private ISNode DeepCloneCore()
             return new C(this);
         }
 
-        private void Init(int integerProperty, int integerPropertyWithDefault, double numberProperty, double numberPropertyWithDefault, string stringProperty, string stringPropertyWithDefault, bool booleanProperty, bool booleanPropertyWithTrueDefault, bool booleanPropertyWithFalseDefault, Color enumeratedPropertyWithDefault, IEnumerable<double> arrayProp, Uri uriProp, DateTime dateTimeProp, D referencedTypeProp, IEnumerable<D> arrayOfRefProp, IEnumerable<IEnumerable<D>> arrayOfArrayProp, IDictionary<string, string> dictionaryProp, IDictionary<string, double> dictionaryWithPrimitiveSchemaProp, IDictionary<string, D> dictionaryWithObjectSchemaProp, IDictionary<string, IList<D>> dictionaryWithObjectArraySchemaProp, IDictionary<Uri, D> dictionaryWithUriKeyProp, IDictionary<string, V> dictionaryWithHintedValueProp)
+        private void Init(int? integerProperty, int integerPropertyWithDefault, double numberProperty, double numberPropertyWithDefault, string stringProperty, string stringPropertyWithDefault, bool booleanProperty, bool booleanPropertyWithTrueDefault, bool booleanPropertyWithFalseDefault, Color enumeratedPropertyWithDefault, IEnumerable<double> arrayProp, Uri uriProp, DateTime dateTimeProp, D referencedTypeProp, IEnumerable<D> arrayOfRefProp, IEnumerable<IEnumerable<D>> arrayOfArrayProp, IDictionary<string, string> dictionaryProp, IDictionary<string, double> dictionaryWithPrimitiveSchemaProp, IDictionary<string, D> dictionaryWithObjectSchemaProp, IDictionary<string, IList<D>> dictionaryWithObjectArraySchemaProp, IDictionary<Uri, D> dictionaryWithUriKeyProp, IDictionary<string, V> dictionaryWithHintedValueProp)
         {
             IntegerProperty = integerProperty;
             IntegerPropertyWithDefault = integerPropertyWithDefault;
@@ -2655,7 +2669,7 @@ public partial class Def2
         public static IComparer<Def2> Comparer => Def2Comparer.Instance;
 
         [DataMember(Name = ""prop2"", IsRequired = false, EmitDefaultValue = false)]
-        public int Prop2 { get; set; }
+        public int? Prop2 { get; set; }
     }
 }";
 
@@ -2704,7 +2718,10 @@ public int GetHashCode(Def2 obj)
             int result = 17;
             unchecked
             {
-                result = (result * 31) + obj.Prop2.GetHashCode();
+                if (obj.Prop2 != null)
+                {
+                    result = (result * 31) + obj.Prop2.GetHashCode();
+                }
             }
 
             return result;
@@ -3268,7 +3285,7 @@ public partial class C
         public static IComparer<C> Comparer => CComparer.Instance;
 
         [DataMember(Name = ""intDefProp"", IsRequired = false, EmitDefaultValue = false)]
-        public int IntDefProp { get; set; }
+        public int? IntDefProp { get; set; }
     }
 }";
             const string ExpectedEqualityComparerClass =
@@ -3316,7 +3333,10 @@ public int GetHashCode(C obj)
             int result = 17;
             unchecked
             {
-                result = (result * 31) + obj.IntDefProp.GetHashCode();
+                if (obj.IntDefProp != null)
+                {
+                    result = (result * 31) + obj.IntDefProp.GetHashCode();
+                }
             }
 
             return result;
@@ -3398,6 +3418,15 @@ public void GeneratesAttributesForPropertiesOfPrimitiveTypeWithDefaults()
       ""description"": ""An integer property with a default value."",
       ""default"": 42
     },
+    ""integerPropertyRequired"": {
+      ""type"": ""integer"",
+      ""description"": ""An integer property, required.""
+    },
+    ""integerPropertyRequiredAndWithDefault"": {
+      ""type"": ""integer"",
+      ""description"": ""An integer property, required and with a default value."",
+      ""default"": 42
+    },
     ""numberProperty"": {
       ""type"": ""number"",
       ""description"": ""A number property.""
@@ -3438,7 +3467,8 @@ public void GeneratesAttributesForPropertiesOfPrimitiveTypeWithDefaults()
       },
       ""default"": []
     }
-  }
+  },
+  ""required"": [ ""integerPropertyRequired"", ""integerPropertyRequiredAndWithDefault"" ]
 }";
             const string ExpectedClass =
 @"using System;
@@ -3458,7 +3488,7 @@ public partial class C
         /// An integer property.
         /// </summary>
         [DataMember(Name = ""integerProperty"", IsRequired = false, EmitDefaultValue = false)]
-        public int IntegerProperty { get; set; }
+        public int? IntegerProperty { get; set; }
 
         /// <summary>
         /// An integer property with a default value.
@@ -3468,6 +3498,20 @@ public partial class C
         [JsonProperty(DefaultValueHandling = DefaultValueHandling.IgnoreAndPopulate)]
         public int IntegerPropertyWithDefault { get; set; }
 
+        /// <summary>
+        /// An integer property, required.
+        /// </summary>
+        [DataMember(Name = ""integerPropertyRequired"", IsRequired = true)]
+        public int IntegerPropertyRequired { get; set; }
+
+        /// <summary>
+        /// An integer property, required and with a default value.
+        /// </summary>
+        [DataMember(Name = ""integerPropertyRequiredAndWithDefault"", IsRequired = true)]
+        [DefaultValue(42)]
+        [JsonProperty(DefaultValueHandling = DefaultValueHandling.IgnoreAndPopulate)]
+        public int IntegerPropertyRequiredAndWithDefault { get; set; }
+
         /// <summary>
         /// A number property.
         /// </summary>
diff --git a/src/Json.Schema.ToDotNet.UnitTests/Hints/AttributeHintTests.cs b/src/Json.Schema.ToDotNet.UnitTests/Hints/AttributeHintTests.cs
index ad7a4ca..c34e449 100644
--- a/src/Json.Schema.ToDotNet.UnitTests/Hints/AttributeHintTests.cs
+++ b/src/Json.Schema.ToDotNet.UnitTests/Hints/AttributeHintTests.cs
@@ -43,7 +43,7 @@ public partial class C
     {
         [DataMember(Name = ""theProperty"", IsRequired = false, EmitDefaultValue = false)]
         [Test]
-        public int TheProperty { get; set; }
+        public int? TheProperty { get; set; }
     }
 }"
             ),
@@ -85,7 +85,7 @@ public partial class C
     {
         [DataMember(Name = ""theProperty"", IsRequired = false, EmitDefaultValue = false)]
         [Test(typeof(string))]
-        public int TheProperty { get; set; }
+        public int? TheProperty { get; set; }
     }
 }"
             ),
@@ -129,7 +129,7 @@ public partial class C
     {
         [DataMember(Name = ""theProperty"", IsRequired = false, EmitDefaultValue = false)]
         [Test(typeof(string), 42, ""a"")]
-        public int TheProperty { get; set; }
+        public int? TheProperty { get; set; }
     }
 }"
             ),
@@ -171,7 +171,7 @@ public partial class C
     {
         [DataMember(Name = ""theProperty"", IsRequired = false, EmitDefaultValue = false)]
         [Test(DefaultValueHandling = DefaultValueHandling.Ignore)]
-        public int TheProperty { get; set; }
+        public int? TheProperty { get; set; }
     }
 }"
             ),
@@ -214,7 +214,7 @@ public partial class C
     {
         [DataMember(Name = ""theProperty"", IsRequired = false, EmitDefaultValue = false)]
         [Test(DefaultValueHandling = DefaultValueHandling.Ignore, DefaultValue = 42)]
-        public int TheProperty { get; set; }
+        public int? TheProperty { get; set; }
     }
 }"
             ),
@@ -260,7 +260,7 @@ public partial class C
         [DataMember(Name = ""theProperty"", IsRequired = false, EmitDefaultValue = false)]
         [Test1]
         [Test2]
-        public int TheProperty { get; set; }
+        public int? TheProperty { get; set; }
     }
 }"
             ),
@@ -301,7 +301,7 @@ public partial class C
     {
         [DataMember(Name = ""theProperty"", IsRequired = false, EmitDefaultValue = false)]
         [Test]
-        public int TheProperty { get; set; }
+        public int? TheProperty { get; set; }
     }
 }"
             ),
diff --git a/src/Json.Schema.ToDotNet.UnitTests/Hints/InterfaceHintTests.cs b/src/Json.Schema.ToDotNet.UnitTests/Hints/InterfaceHintTests.cs
index 285d8b2..c135cc4 100644
--- a/src/Json.Schema.ToDotNet.UnitTests/Hints/InterfaceHintTests.cs
+++ b/src/Json.Schema.ToDotNet.UnitTests/Hints/InterfaceHintTests.cs
@@ -69,13 +69,13 @@ public partial class C : IC
         /// The value.
         /// </summary>
         [DataMember(Name = ""value"", IsRequired = false, EmitDefaultValue = false)]
-        public int Value { get; set; }
+        public int? Value { get; set; }
 
         /// <summary>
         /// Internal value.
         /// </summary>
         [DataMember(Name = ""value2"", IsRequired = false, EmitDefaultValue = false)]
-        internal int Value2 { get; set; }
+        internal int? Value2 { get; set; }
     }
 }",
 
@@ -92,7 +92,7 @@ public partial interface IC
         /// <summary>
         /// The value.
         /// </summary>
-        int Value { get; }
+        int? Value { get; }
     }
 }"
             }
diff --git a/src/Json.Schema.ToDotNet.UnitTests/Hints/PropertyModifiersHintTests.cs b/src/Json.Schema.ToDotNet.UnitTests/Hints/PropertyModifiersHintTests.cs
index 94d6ca9..be2df72 100644
--- a/src/Json.Schema.ToDotNet.UnitTests/Hints/PropertyModifiersHintTests.cs
+++ b/src/Json.Schema.ToDotNet.UnitTests/Hints/PropertyModifiersHintTests.cs
@@ -43,7 +43,7 @@ namespace N
     public partial class C
     {
         [DataMember(Name = ""theProperty"", IsRequired = false, EmitDefaultValue = false)]
-        int TheProperty { get; set; }
+        int? TheProperty { get; set; }
     }
 }"
             ),
@@ -83,7 +83,7 @@ namespace N
     public partial class C
     {
         [DataMember(Name = ""theProperty"", IsRequired = false, EmitDefaultValue = false)]
-        internal int TheProperty { get; set; }
+        internal int? TheProperty { get; set; }
     }
 }"
             ),
@@ -124,7 +124,7 @@ namespace N
     public partial class C
     {
         [DataMember(Name = ""theProperty"", IsRequired = false, EmitDefaultValue = false)]
-        internal override int TheProperty { get; set; }
+        internal override int? TheProperty { get; set; }
     }
 }"
             ),
@@ -194,7 +194,7 @@ namespace N
     public partial class C
     {
         [DataMember(Name = ""theProperty"", IsRequired = false, EmitDefaultValue = false)]
-        internal override int TheProperty { get; set; }
+        internal override int? TheProperty { get; set; }
     }
 }"
             ),
diff --git a/src/Json.Schema.ToDotNet/PropertyInfoDictionary.cs b/src/Json.Schema.ToDotNet/PropertyInfoDictionary.cs
index 45ac8c3..464b7e9 100644
--- a/src/Json.Schema.ToDotNet/PropertyInfoDictionary.cs
+++ b/src/Json.Schema.ToDotNet/PropertyInfoDictionary.cs
@@ -44,6 +44,9 @@ public class PropertyInfoDictionary : IReadOnlyDictionary<string, PropertyInfo>
         // <code>Location{}[]</code> is a dictionary property whose elements are arrays.
         internal const string DictionaryMarker = "{}";
 
+        internal const string IntType = "System.int";
+        internal const string LongType = "System.long";
+        internal const string GuidType = "System.Guid";
         internal const string BigIntegerType = "System.Numerics.BigInteger";
 
         /// <summary>
@@ -234,6 +237,10 @@ private void AddPropertyInfoFromPropertySchema(
             bool isOfSchemaDefinedType = false;
             int arrayRank = 0;
 
+            bool scalarValueTypeNullable = !isRequired && propertySchema.Default == null;
+            HashKind scalarValueTypeHashKind =
+                scalarValueTypeNullable ? HashKind.ScalarReferenceType : HashKind.ScalarValueType;
+
             if (propertySchema.IsDateTime())
             {
                 comparisonKind = ComparisonKind.OperatorEquals;
@@ -251,9 +258,9 @@ private void AddPropertyInfoFromPropertySchema(
             else if (propertySchema.IsUuid())
             {
                 comparisonKind = ComparisonKind.OperatorEquals;
-                hashKind = isRequired ? HashKind.ScalarValueType : HashKind.ScalarReferenceType;
+                hashKind = scalarValueTypeHashKind;
                 initializationKind = InitializationKind.SimpleAssign;
-                type = MakeNamedType(isRequired ? "System.Guid" : "System.Guid?", out namespaceName);
+                type = MakeNamedType(GuidType, out namespaceName, scalarValueTypeNullable);
             }
             else if (propertySchema.ShouldBeDictionary(_typeName, schemaPropertyName, _hintDictionary, out DictionaryHint dictionaryHint))
             {
@@ -280,7 +287,7 @@ private void AddPropertyInfoFromPropertySchema(
                 initializationKind = InitializationKind.SimpleAssign;
                 type = MakeNamedType(referencedEnumTypeName, out namespaceName);
             }
-            else if (propertySchema.ShouldBeEnum(_typeName, schemaPropertyName,  _hintDictionary, out EnumHint enumHint))
+            else if (propertySchema.ShouldBeEnum(_typeName, schemaPropertyName, _hintDictionary, out EnumHint enumHint))
             {
                 comparisonKind = ComparisonKind.OperatorEquals;
                 hashKind = HashKind.ScalarValueType;
@@ -313,14 +320,15 @@ private void AddPropertyInfoFromPropertySchema(
 
                     case SchemaType.Integer:
                         comparisonKind = ComparisonKind.OperatorEquals;
-                        hashKind = HashKind.ScalarValueType;
+                        hashKind = scalarValueTypeHashKind;
                         initializationKind = InitializationKind.SimpleAssign;
                         type = MakeProperIntegerType(_generateJsonIntegerAs,
                             propertySchema.Minimum, propertySchema.ExclusiveMinimum,
                             propertySchema.Maximum, propertySchema.ExclusiveMaximum,
+                            scalarValueTypeNullable,
                             out namespaceName);
                         break;
-                        
+
                     case SchemaType.String:
                         comparisonKind = ComparisonKind.OperatorEquals;
                         hashKind = HashKind.ScalarReferenceType;
@@ -445,8 +453,13 @@ private TypeSyntax MakeObjectTypeFromReference(UriOrFragment reference, out stri
             return MakeNamedType(className, out namespaceName);
         }
 
-        private TypeSyntax MakeNamedType(string typeName, out string namespaceName)
+        private TypeSyntax MakeNamedType(string typeName, out string namespaceName, bool nullable = false)
         {
+            if (nullable)
+            {
+                typeName += "?";
+            }
+
             string unqualifiedTypeName = GetUnqualifiedTypeName(typeName, out namespaceName);
 
             return SyntaxFactory.ParseTypeName(unqualifiedTypeName);
@@ -630,7 +643,9 @@ private string GetUnqualifiedTypeName(string typeName, out string namespaceName)
                 namespaceName = null;
             }
 
-            return unqualifiedTypeName.ToPascalCase();
+            namespaceName = namespaceName == "System" ? null : namespaceName;
+
+            return typeName.StartsWith("System.") ? unqualifiedTypeName : unqualifiedTypeName.ToPascalCase();
         }
 
         private void OnAdditionalTypeRequired(CodeGenHint hint, JsonSchema schema)
@@ -687,6 +702,7 @@ private TypeSyntax GetConcreteType(string propertyName, string interfaceName)
         internal TypeSyntax MakeProperIntegerType(GenerateJsonIntegerOption generateJsonIntegerAs,
             double? minimum, bool? exclusiveMinimum,
             double? maximum, bool? exclusiveMaximum,
+            bool nullable,
             out string namespaceName)
         {
             namespaceName = null;
@@ -694,13 +710,13 @@ internal TypeSyntax MakeProperIntegerType(GenerateJsonIntegerOption generateJson
             switch (generateJsonIntegerAs)
             {
                 case GenerateJsonIntegerOption.Long:
-                    return SyntaxFactory.PredefinedType(SyntaxFactory.Token(SyntaxKind.LongKeyword));
+                    return MakeNamedType(LongType, out namespaceName, nullable);
                 case GenerateJsonIntegerOption.BigInteger:
-                    return MakeNamedType(BigIntegerType, out namespaceName);
+                    return MakeNamedType(BigIntegerType, out namespaceName, nullable);
                 case GenerateJsonIntegerOption.Auto:
                     if (!minimum.HasValue || !maximum.HasValue)
                     {
-                        return MakeNamedType(BigIntegerType, out namespaceName);
+                        return MakeNamedType(BigIntegerType, out namespaceName, nullable);
                     }
 
                     if (exclusiveMinimum == true)
@@ -720,12 +736,12 @@ internal TypeSyntax MakeProperIntegerType(GenerateJsonIntegerOption generateJson
 
                     if (minimum.Value < int.MinValue || maximum.Value > int.MaxValue)
                     {
-                        return SyntaxFactory.PredefinedType(SyntaxFactory.Token(SyntaxKind.LongKeyword));
+                        return MakeNamedType(LongType, out namespaceName, nullable);
                     }
 
-                    return SyntaxFactory.PredefinedType(SyntaxFactory.Token(SyntaxKind.IntKeyword));
+                    return MakeNamedType(IntType, out namespaceName, nullable);
                 default:
-                    return SyntaxFactory.PredefinedType(SyntaxFactory.Token(SyntaxKind.IntKeyword));
+                    return MakeNamedType(IntType, out namespaceName, nullable);
             }
         }
 
diff --git a/src/ReleaseHistory.md b/src/ReleaseHistory.md
index 1c7e697..697ca83 100644
--- a/src/ReleaseHistory.md
+++ b/src/ReleaseHistory.md
@@ -1,6 +1,7 @@
 # Microsoft Json Schema Packages
 
 ## **Unreleased**
+* BREAKING: .NET type to express Json integers now will be nullable if the property is not required and also without default. [#167](https://github.com/microsoft/jschema/pull/167)
 * FEATURE: Add new option for specifying .NET type to express Json numbers: `--generate-json-number-as = double | float | decimal` with a default of `double`. [#166](https://github.com/microsoft/jschema/pull/166)
 
 ## **2.1.0** [Pointer](https://www.nuget.org/packages/Microsoft.Json.Pointer/2.1.0) | [Schema](https://www.nuget.org/packages/Microsoft.Json.Schema/2.1.0)| [Schema.ToDotNet](https://www.nuget.org/packages/Microsoft.Json.Schema.ToDotNet/2.1.0)| [Schema.Validation](https://www.nuget.org/packages/Microsoft.Json.Schema.Validation/2.1.0)