diff --git a/src/Microsoft.OData.Edm/Csdl/Serialization/EdmModelCsdlSchemaJsonWriter.cs b/src/Microsoft.OData.Edm/Csdl/Serialization/EdmModelCsdlSchemaJsonWriter.cs
index d437d42e23..d0d2df6195 100644
--- a/src/Microsoft.OData.Edm/Csdl/Serialization/EdmModelCsdlSchemaJsonWriter.cs
+++ b/src/Microsoft.OData.Edm/Csdl/Serialization/EdmModelCsdlSchemaJsonWriter.cs
@@ -384,10 +384,12 @@ internal override void WriteEnumMemberElementHeader(IEdmEnumMember member)
         /// 7.2.1 Nullable, A Boolean value specifying whether a value is required for the property.
         /// </summary>
         /// <param name="reference">The Edm type reference.</param>
-        internal override void WriteNullableAttribute(IEdmTypeReference reference)
+        /// <param name="parentTypeKind">The parent object's (the property) type kind.
+        internal override void WriteNullableAttribute(IEdmTypeReference reference, EdmTypeKind parentTypeKind)
         {
-            // The value of $Nullable is one of the Boolean literals true or false. Absence of the member means false.
-            this.jsonWriter.WriteOptionalProperty("$Nullable", reference.IsNullable, defaultValue: false);
+            // The value of $Nullable is one of the Boolean literals true or false. Absence of the JSON property means false.
+            // parentTypeKind gets intentionally ignored since JSON CSDL never writes $Nullable=false
+            this.jsonWriter.WriteOptionalProperty("$Nullable", reference.IsNullable, defaultValue: false);            
         }
 
         internal override void WriteTypeDefinitionAttributes(IEdmTypeDefinitionReference reference)
diff --git a/src/Microsoft.OData.Edm/Csdl/Serialization/EdmModelCsdlSchemaWriter.cs b/src/Microsoft.OData.Edm/Csdl/Serialization/EdmModelCsdlSchemaWriter.cs
index 0c3f1f771d..224ed1a39c 100644
--- a/src/Microsoft.OData.Edm/Csdl/Serialization/EdmModelCsdlSchemaWriter.cs
+++ b/src/Microsoft.OData.Edm/Csdl/Serialization/EdmModelCsdlSchemaWriter.cs
@@ -105,7 +105,13 @@ internal virtual void WriteNavigationPropertyBindingsEnd(IEnumerable<IEdmNavigat
             // Nothing here
         }
 
-        internal abstract void WriteNullableAttribute(IEdmTypeReference reference);
+        /// <summary>
+        /// 7.2.1 Nullable, A Boolean value specifying whether a value is required for the property.
+        /// </summary>
+        /// <param name="reference">The Edm type reference.</param>
+        /// <param name="parentTypeKind">The parent object's (the property's) type kind.
+        internal abstract void WriteNullableAttribute(IEdmTypeReference reference, EdmTypeKind parentTypeKind);
+
 
         internal abstract void WriteTypeDefinitionAttributes(IEdmTypeDefinitionReference reference);
 
diff --git a/src/Microsoft.OData.Edm/Csdl/Serialization/EdmModelCsdlSchemaXmlWriter.cs b/src/Microsoft.OData.Edm/Csdl/Serialization/EdmModelCsdlSchemaXmlWriter.cs
index 09ccae1f10..43c5b92fee 100644
--- a/src/Microsoft.OData.Edm/Csdl/Serialization/EdmModelCsdlSchemaXmlWriter.cs
+++ b/src/Microsoft.OData.Edm/Csdl/Serialization/EdmModelCsdlSchemaXmlWriter.cs
@@ -223,9 +223,19 @@ internal override void WriteEnumMemberElementEnd(IEdmEnumMember member)
             this.xmlWriter.WriteEndElement();
         }
 
-        internal override void WriteNullableAttribute(IEdmTypeReference reference)
+        /// <inheritdoc/>
+        internal override void WriteNullableAttribute(IEdmTypeReference reference, EdmTypeKind parentTypeKind)
         {
-            this.WriteOptionalAttribute(CsdlConstants.Attribute_Nullable, reference.IsNullable, CsdlConstants.Default_Nullable, EdmValueWriter.BooleanAsXml);
+            // if the parent type is a collection ensure the XML attribute is always written, even if false.
+            // see section 7.2.1 Nullable of OData 4.0.1
+            if (parentTypeKind == EdmTypeKind.Collection)
+            {
+                this.WriteRequiredAttribute(CsdlConstants.Attribute_Nullable, reference.IsNullable, EdmValueWriter.BooleanAsXml);
+            }
+            else
+            {
+                this.WriteOptionalAttribute(CsdlConstants.Attribute_Nullable, reference.IsNullable, CsdlConstants.Default_Nullable, EdmValueWriter.BooleanAsXml);
+            }
         }
 
         internal override void WriteTypeDefinitionAttributes(IEdmTypeDefinitionReference reference)
diff --git a/src/Microsoft.OData.Edm/Csdl/Serialization/EdmModelCsdlSerializationVisitor.cs b/src/Microsoft.OData.Edm/Csdl/Serialization/EdmModelCsdlSerializationVisitor.cs
index 45b618822f..9c9a4dfacc 100644
--- a/src/Microsoft.OData.Edm/Csdl/Serialization/EdmModelCsdlSerializationVisitor.cs
+++ b/src/Microsoft.OData.Edm/Csdl/Serialization/EdmModelCsdlSerializationVisitor.cs
@@ -156,7 +156,10 @@ protected override void ProcessEntityType(IEdmEntityType element)
         protected override void ProcessStructuralProperty(IEdmStructuralProperty element)
         {
             bool inlineType = IsInlineType(element.Type);
-            this.BeginElement(element, (IEdmStructuralProperty t) => { this.schemaWriter.WriteStructuralPropertyElementHeader(t, inlineType); }, e => { this.ProcessFacets(e.Type, inlineType); });
+            this.BeginElement(element, 
+                (IEdmStructuralProperty t) => { this.schemaWriter.WriteStructuralPropertyElementHeader(t, inlineType); },
+                e => { this.ProcessFacets(e.Type, inlineType, true); }
+            );
             if (!inlineType)
             {
                 VisitTypeReference(element.Type);
@@ -243,7 +246,7 @@ protected override void ProcessTypeDefinition(IEdmTypeDefinition element)
         protected override void ProcessTerm(IEdmTerm term)
         {
             bool inlineType = term.Type != null && IsInlineType(term.Type);
-            this.BeginElement(term, (IEdmTerm t) => { this.schemaWriter.WriteTermElementHeader(t, inlineType); }, e => { this.ProcessFacets(e.Type, inlineType); });
+            this.BeginElement(term, (IEdmTerm t) => { this.schemaWriter.WriteTermElementHeader(t, inlineType); }, e => { this.ProcessFacets(e.Type, inlineType, false); });
             if (!inlineType)
             {
                 if (term.Type != null)
@@ -271,7 +274,7 @@ protected override void ProcessOperationParameter(IEdmOperationParameter element
             this.BeginElement(
                 element,
                 (IEdmOperationParameter t) => { this.schemaWriter.WriteOperationParameterElementHeader(t, inlineType); },
-                e => { this.ProcessFacets(e.Type, inlineType); });
+                e => { this.ProcessFacets(e.Type, inlineType, false); });
             if (!inlineType)
             {
                 VisitTypeReference(element.Type);
@@ -303,7 +306,7 @@ protected override void ProcessOperationReturn(IEdmOperationReturn operationRetu
                     if (inlineType)
                     {
                         this.schemaWriter.WriteTypeAttribute(type);
-                        this.ProcessFacets(type, true /*inlineType*/);
+                        this.ProcessFacets(type, true /*inlineType*/, false);
                     }
                     else
                     {
@@ -319,7 +322,7 @@ protected override void ProcessCollectionType(IEdmCollectionType element)
             this.BeginElement(
                 element,
                 (IEdmCollectionType t) => this.schemaWriter.WriteCollectionTypeElementHeader(t, inlineType),
-                e => this.ProcessFacets(e.ElementType, inlineType));
+                e => this.ProcessFacets(e.ElementType, inlineType, false));
             if (!inlineType)
             {
                 VisitTypeReference(element.ElementType);
@@ -439,7 +442,7 @@ protected override void ProcessIsTypeExpression(IEdmIsTypeExpression expression)
 
             if (this.isXml)
             {
-                this.BeginElement(expression, (IEdmIsTypeExpression t) => { this.schemaWriter.WriteIsTypeExpressionElementHeader(t, inlineType); }, e => { this.ProcessFacets(e.Type, inlineType); });
+                this.BeginElement(expression, (IEdmIsTypeExpression t) => { this.schemaWriter.WriteIsTypeExpressionElementHeader(t, inlineType); }, e => { this.ProcessFacets(e.Type, inlineType, false); });
                 if (!inlineType)
                 {
                     VisitTypeReference(expression.Type);
@@ -453,7 +456,7 @@ protected override void ProcessIsTypeExpression(IEdmIsTypeExpression expression)
                 this.BeginElement(expression, (IEdmIsTypeExpression t) => { this.schemaWriter.WriteIsTypeExpressionElementHeader(t, inlineType); });
                 this.VisitExpression(expression.Operand);
                 this.schemaWriter.WriteIsOfExpressionType(expression, inlineType);
-                this.ProcessFacets(expression.Type, inlineType);
+                this.ProcessFacets(expression.Type, inlineType, false);
                 this.EndElement(expression);
             }
         }
@@ -533,7 +536,7 @@ protected override void ProcessCastExpression(IEdmCastExpression expression)
 
             if (this.isXml)
             {
-                this.BeginElement(expression, (IEdmCastExpression t) => { this.schemaWriter.WriteCastExpressionElementHeader(t, inlineType); }, e => { this.ProcessFacets(e.Type, inlineType); });
+                this.BeginElement(expression, (IEdmCastExpression t) => { this.schemaWriter.WriteCastExpressionElementHeader(t, inlineType); }, e => { this.ProcessFacets(e.Type, inlineType, false); });
                 if (!inlineType)
                 {
                     VisitTypeReference(expression.Type);
@@ -549,7 +552,7 @@ protected override void ProcessCastExpression(IEdmCastExpression expression)
                 this.VisitExpression(expression.Operand);
 
                 this.schemaWriter.WriteCastExpressionType(expression, inlineType);
-                this.ProcessFacets(expression.Type, inlineType);
+                this.ProcessFacets(expression.Type, inlineType, false);
 
                 this.EndElement(expression, t => this.schemaWriter.WriteCastExpressionElementEnd(t, inlineType));
             }
@@ -653,7 +656,7 @@ private void ProcessReferentialConstraint(IEdmReferentialConstraint element)
             }
         }
 
-        private void ProcessFacets(IEdmTypeReference element, bool inlineType)
+        private void ProcessFacets(IEdmTypeReference element, bool inlineType, bool nullableAttributeRequiredForCollection)
         {
             if (element != null)
             {
@@ -665,15 +668,16 @@ private void ProcessFacets(IEdmTypeReference element, bool inlineType)
 
                 if (inlineType)
                 {
-                    if (element.TypeKind() == EdmTypeKind.Collection)
+                    var typeKind = element.TypeKind();
+                    if (typeKind == EdmTypeKind.Collection)
                     {
-                        IEdmCollectionTypeReference collectionElement = element.AsCollection();
-                        this.schemaWriter.WriteNullableAttribute(collectionElement.CollectionDefinition().ElementType);
-                        VisitTypeReference(collectionElement.CollectionDefinition().ElementType);
+                        var elementType = element.AsCollection().CollectionDefinition().ElementType;
+                        this.schemaWriter.WriteNullableAttribute(elementType, typeKind);
+                        VisitTypeReference(elementType);
                     }
                     else
                     {
-                        this.schemaWriter.WriteNullableAttribute(element);
+                        this.schemaWriter.WriteNullableAttribute(element, typeKind);
                         VisitTypeReference(element);
                     }
                 }
diff --git a/test/FunctionalTests/Microsoft.OData.Edm.Tests/Csdl/CsdlWriterTests.cs b/test/FunctionalTests/Microsoft.OData.Edm.Tests/Csdl/CsdlWriterTests.cs
index 8e2d314e66..3be5048ae8 100644
--- a/test/FunctionalTests/Microsoft.OData.Edm.Tests/Csdl/CsdlWriterTests.cs
+++ b/test/FunctionalTests/Microsoft.OData.Edm.Tests/Csdl/CsdlWriterTests.cs
@@ -311,7 +311,8 @@ public void WriteNavigationPropertyInComplexType()
       },
       ""Addresses"": {
         ""$Collection"": true,
-        ""$Type"": ""DefaultNs.Address""
+        ""$Type"": ""DefaultNs.Address"",
+        ""$Nullable"": false
       }
     },
     ""City"": {
@@ -745,7 +746,7 @@ public void SetNavigationPropertyPartnerTest()
       },
       ""ComplexProp"": {
         ""$Collection"": true,
-        ""$Type"": ""NS.ComplexType1""
+        ""$Type"": ""NS.ComplexType1"",
       },
       ""OuterNavA"": {
         ""$Kind"": ""NavigationProperty"",
@@ -1421,7 +1422,7 @@ public void ShouldWriteEdmPathTypeProperty()
                 "<edmx:DataServices>" +
                   "<Schema Namespace=\"NS\" xmlns=\"http://docs.oasis-open.org/odata/ns/edm\">" +
                     "<ComplexType Name=\"SelectType\">" +
-                      "<Property Name=\"DefaultSelect\" Type=\"Collection(Edm.PropertyPath)\" />" +
+                      "<Property Name=\"DefaultSelect\" Type=\"Collection(Edm.PropertyPath)\" Nullable=\"true\" />" +
                       "<Property Name=\"DefaultHidden\" Type=\"Collection(Edm.NavigationPropertyPath)\" Nullable=\"false\" />" +
                     "</ComplexType>" +
                     "<Term Name=\"MyTerm\" Type=\"NS.SelectType\" />" +
@@ -1442,7 +1443,8 @@ public void ShouldWriteEdmPathTypeProperty()
       },
       ""DefaultHidden"": {
         ""$Collection"": true,
-        ""$Type"": ""Edm.NavigationPropertyPath""
+        ""$Type"": ""Edm.NavigationPropertyPath"",
+        ""$Nullable"": false
       }
     },
     ""MyTerm"": {
@@ -1604,8 +1606,8 @@ public void CanWriteEdmEntityTypeWithCollectionAbstractTypeButValidationFailed()
                         "<PropertyRef Name=\"Id\" />" +
                       "</Key>" +
                       "<Property Name=\"Id\" Type=\"Edm.Int32\" Nullable=\"false\" />" +
-                      "<Property Name=\"Primitive\" Type=\"Collection(Edm.PrimitiveType)\" />" +
-                      "<Property Name=\"Complex\" Type=\"Collection(Edm.ComplexType)\" />" +
+                      "<Property Name=\"Primitive\" Type=\"Collection(Edm.PrimitiveType)\" Nullable=\"true\" />" +
+                      "<Property Name=\"Complex\" Type=\"Collection(Edm.ComplexType)\" Nullable=\"true\" />" +
                     "</EntityType>" +
                   "</Schema>" +
                 "</edmx:DataServices>" +
@@ -2377,7 +2379,7 @@ public void CanWriteEdmModelWithUntypedProperty()
                         "</Key>" +
                         "<Property Name=\"Id\" Type=\"Edm.String\" />" +
                         "<Property Name=\"Value\" Type=\"Edm.Untyped\" />" +
-                        "<Property Name=\"Data\" Type=\"Collection(Edm.Untyped)\" />" +
+                        "<Property Name=\"Data\" Type=\"Collection(Edm.Untyped)\" Nullable=\"true\" />" +
                       "</EntityType>" +
                     "</Schema>" +
                   "</edmx:DataServices>" +
diff --git a/test/FunctionalTests/Microsoft.OData.Edm.Tests/Csdl/Serialization/EdmModelCsdlSerializationVisitorTests.cs b/test/FunctionalTests/Microsoft.OData.Edm.Tests/Csdl/Serialization/EdmModelCsdlSerializationVisitorTests.cs
index 2946095263..afb1e2abf3 100644
--- a/test/FunctionalTests/Microsoft.OData.Edm.Tests/Csdl/Serialization/EdmModelCsdlSerializationVisitorTests.cs
+++ b/test/FunctionalTests/Microsoft.OData.Edm.Tests/Csdl/Serialization/EdmModelCsdlSerializationVisitorTests.cs
@@ -93,7 +93,7 @@ public void VerifyComplexTypeWithNavigationPropertiesWrittenCorrectly()
             // Act & Assert for XML
             VisitAndVerifyXml(v => v.VisitSchemaType(complexType),
                 @"<ComplexType Name=""Address"">
-  <Property Name=""Street"" Type=""Collection(Edm.String)"" MaxLength=""42"" Unicode=""false"" />
+  <Property Name=""Street"" Type=""Collection(Edm.String)"" Nullable=""true"" MaxLength=""42"" Unicode=""false"" />
   <NavigationProperty Name=""City"" Type=""NS.City"" Nullable=""false"" ContainsTarget=""true"">
     <OnDelete Action=""Cascade"" />
   </NavigationProperty>
@@ -216,7 +216,8 @@ public void VerifyEntityTypeWithNavigationPropertiesWrittenCorrectly()
     ""$Kind"": ""EntityType"",
     ""Locations"": {
       ""$Collection"": true,
-      ""$Type"": ""NS.Address""
+      ""$Type"": ""NS.Address"",
+      ""$Nullable"": false
     },
     ""Orders"": {
       ""$Kind"": ""NavigationProperty"",
@@ -2015,6 +2016,53 @@ public void VerifyAnnotationWithRecordExpressionWrittenCorrectly()
         }
         #endregion
 
+        #region Collection Type References
+        [Fact]
+        public void VerifyCollectionTypeReferencesWrittenCorrectly()
+        {
+            // see https://github.com/OData/odata.net/issues/2028
+            // Arrange
+            EdmComplexType structuredType = new EdmComplexType("NS", "Customer");
+            structuredType.AddStructuralProperty("test01", EdmCoreModel.GetCollection(EdmCoreModel.Instance.GetDecimal(true)));
+            structuredType.AddStructuralProperty("test02", EdmCoreModel.GetCollection(EdmCoreModel.Instance.GetDecimal(false)));
+            structuredType.AddStructuralProperty("test03", EdmCoreModel.Instance.GetDecimal(true));
+            structuredType.AddStructuralProperty("test04", EdmCoreModel.Instance.GetDecimal(false));
+
+            // Act & Assert for XML
+            VisitAndVerifyXml(v => v.VisitSchemaType(structuredType), @"<ComplexType Name=""Customer"">
+  <Property Name=""test01"" Type=""Collection(Edm.Decimal)"" Nullable=""true"" />
+  <Property Name=""test02"" Type=""Collection(Edm.Decimal)"" Nullable=""false"" />
+  <Property Name=""test03"" Type=""Edm.Decimal"" />
+  <Property Name=""test04"" Type=""Edm.Decimal"" Nullable=""false"" />
+</ComplexType>"
+);
+
+            // Act & Assert for JSON
+            VisitAndVerifyJson(v => v.VisitSchemaType(structuredType), @"{
+  ""Customer"": {
+    ""$Kind"": ""ComplexType"",
+    ""test01"": {
+      ""$Collection"": true,
+      ""$Type"": ""Edm.Decimal"",
+      ""$Nullable"": true
+    },
+    ""test02"": {
+      ""$Collection"": true,
+      ""$Type"": ""Edm.Decimal"",
+      ""$Nullable"": false
+    },
+    ""test03"": {
+      ""$Type"": ""Edm.Decimal"",
+      ""$Nullable"": true
+    },
+    ""test04"": {
+      ""$Type"": ""Edm.Decimal""
+    }
+  }
+}");
+        }
+        #endregion
+
         internal void VisitAndVerifyXml(Action<EdmModelCsdlSerializationVisitor> testAction, string expected, bool indent = true)
         {
             XmlWriter xmlWriter;
diff --git a/test/FunctionalTests/Microsoft.OData.Edm.Tests/Vocabularies/AlternateKeysVocabularyTests.cs b/test/FunctionalTests/Microsoft.OData.Edm.Tests/Vocabularies/AlternateKeysVocabularyTests.cs
index b28c58e501..0b678cb01c 100644
--- a/test/FunctionalTests/Microsoft.OData.Edm.Tests/Vocabularies/AlternateKeysVocabularyTests.cs
+++ b/test/FunctionalTests/Microsoft.OData.Edm.Tests/Vocabularies/AlternateKeysVocabularyTests.cs
@@ -27,7 +27,7 @@ public void TestAlternateKeysVocabularyModel()
             const string expectedText = @"<?xml version=""1.0"" encoding=""utf-16""?>
 <Schema Namespace=""OData.Community.Keys.V1"" Alias=""Keys"" xmlns=""http://docs.oasis-open.org/odata/ns/edm"">
   <ComplexType Name=""AlternateKey"">
-    <Property Name=""Key"" Type=""Collection(Keys.PropertyRef)"">
+    <Property Name=""Key"" Type=""Collection(Keys.PropertyRef)"" Nullable=""true"">
       <Annotation Term=""Core.Description"" String=""The set of properties that make up this key"" />
     </Property>
   </ComplexType>
diff --git a/test/FunctionalTests/Microsoft.OData.Edm.Tests/Vocabularies/CapabilitiesVocabularyTests.cs b/test/FunctionalTests/Microsoft.OData.Edm.Tests/Vocabularies/CapabilitiesVocabularyTests.cs
index 3766a956b4..e30718f853 100644
--- a/test/FunctionalTests/Microsoft.OData.Edm.Tests/Vocabularies/CapabilitiesVocabularyTests.cs
+++ b/test/FunctionalTests/Microsoft.OData.Edm.Tests/Vocabularies/CapabilitiesVocabularyTests.cs
@@ -304,7 +304,7 @@ public void TestCapabilitiesVocabularyModel()
     <Property Name=""TypecastSegmentSupported"" Type=""Edm.Boolean"" DefaultValue=""true"" Nullable=""false"">
       <Annotation Term=""Core.Description"" String=""Entities of a specific derived type can be created by specifying a type-cast segment"" />
     </Property>
-    <Property Name=""Permissions"" Type=""Collection(Capabilities.PermissionType)"">
+    <Property Name=""Permissions"" Type=""Collection(Capabilities.PermissionType)"" Nullable=""true"">
       <Annotation Term=""Core.Description"" String=""Required permissions. One of the specified sets of scopes is required to perform the insert."" />
     </Property>
     <Property Name=""QueryOptions"" Type=""Capabilities.ModificationQueryOptionsType"">
@@ -372,7 +372,7 @@ public void TestCapabilitiesVocabularyModel()
     <Property Name=""MaxLevels"" Type=""Edm.Int32"" DefaultValue=""-1"" Nullable=""false"">
       <Annotation Term=""Core.Description"" String=""The maximum number of navigation properties that can be traversed when addressing the collection or entity to update. A value of -1 indicates there is no restriction."" />
     </Property>
-    <Property Name=""Permissions"" Type=""Collection(Capabilities.PermissionType)"">
+    <Property Name=""Permissions"" Type=""Collection(Capabilities.PermissionType)"" Nullable=""true"">
       <Annotation Term=""Core.Description"" String=""Required permissions. One of the specified sets of scopes is required to perform the update."" />
     </Property>
     <Property Name=""QueryOptions"" Type=""Capabilities.ModificationQueryOptionsType"">
@@ -417,7 +417,7 @@ public void TestCapabilitiesVocabularyModel()
     <Property Name=""TypecastSegmentSupported"" Type=""Edm.Boolean"" DefaultValue=""true"" Nullable=""false"">
       <Annotation Term=""Core.Description"" String=""Members of collections can be updated via a PATCH request with a type-cast segment and a `/$each` segment"" />
     </Property>
-    <Property Name=""Permissions"" Type=""Collection(Capabilities.PermissionType)"">
+    <Property Name=""Permissions"" Type=""Collection(Capabilities.PermissionType)"" Nullable=""true"">
       <Annotation Term=""Core.Description"" String=""Required permissions. One of the specified sets of scopes is required to perform the delete."" />
     </Property>
     <Property Name=""CustomHeaders"" Type=""Collection(Capabilities.CustomParameter)"" Nullable=""false"">
@@ -476,7 +476,7 @@ public void TestCapabilitiesVocabularyModel()
     <Property Name=""FilterSegmentSupported"" Type=""Edm.Boolean"" DefaultValue=""true"" Nullable=""false"">
       <Annotation Term=""Core.Description"" String=""Bound action or function can be invoked on a collection-valued binding parameter path with a `/$filter(...)` segment"" />
     </Property>
-    <Property Name=""Permissions"" Type=""Collection(Capabilities.PermissionType)"">
+    <Property Name=""Permissions"" Type=""Collection(Capabilities.PermissionType)"" Nullable=""true"">
       <Annotation Term=""Core.Description"" String=""Required permissions. One of the specified sets of scopes is required to invoke an action or function"" />
     </Property>
     <Property Name=""CustomHeaders"" Type=""Collection(Capabilities.CustomParameter)"" Nullable=""false"">
@@ -510,7 +510,7 @@ public void TestCapabilitiesVocabularyModel()
     <Property Name=""Readable"" Type=""Edm.Boolean"" DefaultValue=""true"" Nullable=""false"">
       <Annotation Term=""Core.Description"" String=""Entities can be retrieved"" />
     </Property>
-    <Property Name=""Permissions"" Type=""Collection(Capabilities.PermissionType)"">
+    <Property Name=""Permissions"" Type=""Collection(Capabilities.PermissionType)"" Nullable=""true"">
       <Annotation Term=""Core.Description"" String=""Required permissions. One of the specified sets of scopes is required to read."" />
     </Property>
     <Property Name=""CustomHeaders"" Type=""Collection(Capabilities.CustomParameter)"" Nullable=""false"">
diff --git a/test/FunctionalTests/Tests/DataEdmLib/FunctionalTests/CsdlSerializingTests.cs b/test/FunctionalTests/Tests/DataEdmLib/FunctionalTests/CsdlSerializingTests.cs
index c98816164f..b8ef503853 100644
--- a/test/FunctionalTests/Tests/DataEdmLib/FunctionalTests/CsdlSerializingTests.cs
+++ b/test/FunctionalTests/Tests/DataEdmLib/FunctionalTests/CsdlSerializingTests.cs
@@ -153,11 +153,11 @@ public void SerializeComplexCollectionProperty()
   </ComplexType>
   <ComplexType Name=""Smod"">
     <Property Name=""Id"" Type=""Edm.Int32"" />
-    <Property Name=""myBinary"" Type=""Collection(Edm.Binary)"" MaxLength=""64"" />
-    <Property Name=""myBinaryMax"" Type=""Collection(Edm.Binary)"" MaxLength=""max"" />
-    <Property Name=""myBoolean"" Type=""Collection(Edm.Boolean)"" />
-    <Property Name=""myEnum"" Type=""Collection(Grumble.Color)"" />
-    <Property Name=""myComplex"" Type=""Collection(Grumble.Foo)"" />
+    <Property Name=""myBinary"" Type=""Collection(Edm.Binary)"" Nullable=""true"" MaxLength=""64"" />
+    <Property Name=""myBinaryMax"" Type=""Collection(Edm.Binary)"" Nullable=""true"" MaxLength=""max"" />
+    <Property Name=""myBoolean"" Type=""Collection(Edm.Boolean)"" Nullable=""true""/>
+    <Property Name=""myEnum"" Type=""Collection(Grumble.Color)"" Nullable=""true"" />
+    <Property Name=""myComplex"" Type=""Collection(Grumble.Foo)"" Nullable=""true"" />
   </ComplexType>
   <EnumType Name=""Color"" IsFlags=""true"">
     <Member Name=""Red"" />
@@ -372,7 +372,7 @@ public void SerializeMultipleFilesDottedNamespace()
     <Property Name=""Address"" Type=""Edm.String"" MaxLength=""2048"" />
   </ComplexType>
 </Schema>";
-            VerifyRoundTrip(new string[] {inputText1, inputText2});
+            VerifyRoundTrip(new string[] { inputText1, inputText2 });
         }
 
         [TestMethod]
@@ -543,7 +543,7 @@ public void FailSerializingTwoSchemasToOneFile()
 
             using (XmlWriter xw = XmlWriter.Create(sw, settings))
             {
-                IEnumerable<EdmError> expectedSerializationErrors = new EdmLibTestErrors() 
+                IEnumerable<EdmError> expectedSerializationErrors = new EdmLibTestErrors()
                 {
                     {0, 0, EdmErrorCode.SingleFileExpected},
                 };
@@ -566,7 +566,7 @@ public void SerializeCollectionReturnTypesRegressionTest()
     <Property Name=""Property1"" Type=""Edm.String"" Nullable=""false"" />
   </EntityType>
   <Function Name=""MyFunction"">
-    <ReturnType Type=""Collection(MyNamespace.MyEntityType)"" />
+    <ReturnType Type=""Collection(MyNamespace.MyEntityType)"" Nullable=""true"" />
   </Function>
 </Schema>";
             VerifyRoundTrip(inputText);
@@ -699,7 +699,7 @@ public void SerializeTerm()
 
             VerifyRoundTrip(inputText);
         }
-        
+
         [TestMethod]
         public void SerializeWithCoreVocabularyTerm()
         {
@@ -1396,10 +1396,10 @@ public void SerializeUsingAlias()
                 </ComplexType>
               </Schema>")};
 
-            var actualCsdls = this.GetSerializerResult(this.GetParserResult(expectedCsdls)).Select(n=>XElement.Parse(n));
+            var actualCsdls = this.GetSerializerResult(this.GetParserResult(expectedCsdls)).Select(n => XElement.Parse(n));
             Assert.IsTrue
                 (
-                    XElement.DeepEquals( GetCsdl(expectedCsdls, "DefaultNamespace"), GetCsdl(actualCsdls, "DefaultNamespace")) && XElement.DeepEquals( GetCsdl(expectedCsdls, "Org.OData.Display"), GetCsdl(actualCsdls, "Org.OData.Display")), 
+                    XElement.DeepEquals(GetCsdl(expectedCsdls, "DefaultNamespace"), GetCsdl(actualCsdls, "DefaultNamespace")) && XElement.DeepEquals(GetCsdl(expectedCsdls, "Org.OData.Display"), GetCsdl(actualCsdls, "Org.OData.Display")),
                     "The CSDLs that the serializer generates is different from the original CSDLs"
                 );
         }
@@ -1433,7 +1433,7 @@ public void RoundtripModelWithTypeDefinitions()
             VerifyRoundTrip(csdl);
         }
 
-        [ TestMethod]
+        [TestMethod]
         public void RoundtripModelWithTypeDefinitionFacets()
         {
             const string csdl = @"<?xml version=""1.0"" encoding=""utf-16""?>