diff --git a/src/Microsoft.OpenApi/Attributes/TrimmingAttributes.cs b/src/Microsoft.OpenApi/Attributes/TrimmingAttributes.cs
index 538ed521e..e93686ddd 100644
--- a/src/Microsoft.OpenApi/Attributes/TrimmingAttributes.cs
+++ b/src/Microsoft.OpenApi/Attributes/TrimmingAttributes.cs
@@ -1,8 +1,6 @@
 // Copyright (c) Microsoft Corporation. All rights reserved.
 // Licensed under the MIT license.
 
-#nullable enable
-
 // This collection of attribute definitions are helpers for accessing trim-related attributes in
 // projects targeting .NET 6 or lower. Since the trimmer queries for these attributes by name, having
 // these attributes source included is sufficient for the trimmer to recognize them. For more information
diff --git a/src/Microsoft.OpenApi/Extensions/OpenApiTypeMapper.cs b/src/Microsoft.OpenApi/Extensions/OpenApiTypeMapper.cs
index 3ae417022..9d6dc60d0 100644
--- a/src/Microsoft.OpenApi/Extensions/OpenApiTypeMapper.cs
+++ b/src/Microsoft.OpenApi/Extensions/OpenApiTypeMapper.cs
@@ -14,7 +14,6 @@ namespace Microsoft.OpenApi.Extensions
     /// </summary>
     public static class OpenApiTypeMapper
     {
-#nullable enable
         /// <summary>
         /// Maps a JsonSchema data type to an identifier.
         /// </summary>
@@ -75,8 +74,6 @@ internal static string ToSingleIdentifier(this JsonSchemaType schemaType)
             return schemaType.ToIdentifiersInternal().Single();
         }
 
-#nullable restore
-
         /// <summary>
         /// Converts a schema type's identifier into the enum equivalent
         /// </summary>
diff --git a/src/Microsoft.OpenApi/Models/OpenApiComponents.cs b/src/Microsoft.OpenApi/Models/OpenApiComponents.cs
index 540664ae5..c3b762088 100644
--- a/src/Microsoft.OpenApi/Models/OpenApiComponents.cs
+++ b/src/Microsoft.OpenApi/Models/OpenApiComponents.cs
@@ -9,8 +9,6 @@
 using Microsoft.OpenApi.Models.References;
 using Microsoft.OpenApi.Writers;
 
-#nullable enable
-
 namespace Microsoft.OpenApi.Models
 {
     /// <summary>
diff --git a/src/Microsoft.OpenApi/Models/OpenApiDocument.cs b/src/Microsoft.OpenApi/Models/OpenApiDocument.cs
index 0f69409d6..e5f82e9cb 100644
--- a/src/Microsoft.OpenApi/Models/OpenApiDocument.cs
+++ b/src/Microsoft.OpenApi/Models/OpenApiDocument.cs
@@ -17,8 +17,6 @@
 using Microsoft.OpenApi.Services;
 using Microsoft.OpenApi.Writers;
 
-#nullable enable
-
 namespace Microsoft.OpenApi.Models
 {
     /// <summary>
diff --git a/src/Microsoft.OpenApi/Models/OpenApiMediaType.cs b/src/Microsoft.OpenApi/Models/OpenApiMediaType.cs
index 7ba469bc6..4c08ccccb 100644
--- a/src/Microsoft.OpenApi/Models/OpenApiMediaType.cs
+++ b/src/Microsoft.OpenApi/Models/OpenApiMediaType.cs
@@ -10,8 +10,6 @@
 using Microsoft.OpenApi.Models.Interfaces;
 using Microsoft.OpenApi.Writers;
 
-#nullable enable
-
 namespace Microsoft.OpenApi.Models
 {
     /// <summary>
diff --git a/src/Microsoft.OpenApi/Models/OpenApiOperation.cs b/src/Microsoft.OpenApi/Models/OpenApiOperation.cs
index 5375fb031..23a98f3d2 100644
--- a/src/Microsoft.OpenApi/Models/OpenApiOperation.cs
+++ b/src/Microsoft.OpenApi/Models/OpenApiOperation.cs
@@ -9,8 +9,6 @@
 using Microsoft.OpenApi.Models.References;
 using Microsoft.OpenApi.Writers;
 
-#nullable enable
-
 namespace Microsoft.OpenApi.Models
 {
     /// <summary>
diff --git a/src/Microsoft.OpenApi/Models/OpenApiReference.cs b/src/Microsoft.OpenApi/Models/OpenApiReference.cs
index ae79cc10f..0e05ec89d 100644
--- a/src/Microsoft.OpenApi/Models/OpenApiReference.cs
+++ b/src/Microsoft.OpenApi/Models/OpenApiReference.cs
@@ -281,10 +281,8 @@ internal void EnsureHostDocumentIsSet(OpenApiDocument currentDocument)
             Utils.CheckArgumentNull(currentDocument);
             hostDocument ??= currentDocument;
         }
-        #nullable enable
         private static string? GetPropertyValueFromNode(JsonObject jsonObject, string key) =>
         jsonObject.TryGetPropertyValue(key, out var valueNode) && valueNode is JsonValue valueCast && valueCast.TryGetValue<string>(out var strValue) ? strValue : null;
-        #nullable restore
         internal void SetSummaryAndDescriptionFromMapNode(MapNode mapNode)
         {
             var (description, summary) = mapNode.JsonNode switch {
diff --git a/src/Microsoft.OpenApi/OpenApiTagComparer.cs b/src/Microsoft.OpenApi/OpenApiTagComparer.cs
index 6652dd5ba..dfa89e87f 100644
--- a/src/Microsoft.OpenApi/OpenApiTagComparer.cs
+++ b/src/Microsoft.OpenApi/OpenApiTagComparer.cs
@@ -4,7 +4,6 @@
 
 namespace Microsoft.OpenApi;
 
-#nullable enable
 /// <summary>
 /// This comparer is used to maintain a globally unique list of tags encountered
 /// in a particular OpenAPI document.
@@ -44,4 +43,3 @@ public bool Equals(IOpenApiTag? x, IOpenApiTag? y)
     /// <inheritdoc/>
     public int GetHashCode(IOpenApiTag obj) => string.IsNullOrEmpty(obj?.Name) ? 0 : StringComparer.GetHashCode(obj!.Name);
 }
-#nullable restore
diff --git a/src/Microsoft.OpenApi/Services/OpenApiWalker.cs b/src/Microsoft.OpenApi/Services/OpenApiWalker.cs
index cf07356d3..49ac98079 100644
--- a/src/Microsoft.OpenApi/Services/OpenApiWalker.cs
+++ b/src/Microsoft.OpenApi/Services/OpenApiWalker.cs
@@ -130,7 +130,6 @@ internal void Walk(OpenApiExternalDocs? externalDocs)
 
             _visitor.Visit(externalDocs);
         }
-#nullable enable
         /// <summary>
         /// Visits <see cref="OpenApiComponents"/> and child objects
         /// </summary>
@@ -256,7 +255,6 @@ internal void Walk(OpenApiComponents? components)
             Walk(components as IOpenApiExtensible);
         }
 
-#nullable restore
         /// <summary>
         /// Visits <see cref="OpenApiPaths"/> and child objects
         /// </summary>
diff --git a/src/Microsoft.OpenApi/Services/OpenApiWorkspace.cs b/src/Microsoft.OpenApi/Services/OpenApiWorkspace.cs
index d668626db..a8ffde23d 100644
--- a/src/Microsoft.OpenApi/Services/OpenApiWorkspace.cs
+++ b/src/Microsoft.OpenApi/Services/OpenApiWorkspace.cs
@@ -281,7 +281,6 @@ public bool Contains(string location)
             return _IOpenApiReferenceableRegistry.ContainsKey(key) || _artifactsRegistry.ContainsKey(key);
         }
 
-#nullable enable
         /// <summary>
         /// Resolves a reference given a key.
         /// </summary>
@@ -307,7 +306,6 @@ public bool Contains(string location)
 
             return default;
         }
-#nullable restore
 
         private Uri? ToLocationUrl(string location)
         {
diff --git a/src/Microsoft.OpenApi/Writers/OpenApiWriterExtensions.cs b/src/Microsoft.OpenApi/Writers/OpenApiWriterExtensions.cs
index ad84d5537..3df27f6d7 100644
--- a/src/Microsoft.OpenApi/Writers/OpenApiWriterExtensions.cs
+++ b/src/Microsoft.OpenApi/Writers/OpenApiWriterExtensions.cs
@@ -126,7 +126,6 @@ public static void WriteProperty<T>(this IOpenApiWriter writer, string name, T v
             writer.WriteValue(value);
         }
 
-#nullable enable
         /// <summary>
         /// Write the optional Open API object/element.
         /// </summary>
@@ -179,7 +178,6 @@ public static void WriteRequiredObject<T>(
                 writer.WriteEndObject();
             }
         }
-#nullable restore
 
         /// <summary>
         /// Write the optional of collection string.