diff --git a/src/Antiforgery/ref/Directory.Build.props b/src/Antiforgery/ref/Directory.Build.props
new file mode 100644
index 0000000000..5001ef12be
--- /dev/null
+++ b/src/Antiforgery/ref/Directory.Build.props
@@ -0,0 +1,7 @@
+<Project>
+  <Import Project="$([MSBuild]::GetDirectoryNameOfFileAbove($(MSBuildThisFileDirectory)..\, Directory.Build.props))\Directory.Build.props" />
+
+  <PropertyGroup>
+    <Nullable>annotations</Nullable>
+  </PropertyGroup>
+</Project>
\ No newline at end of file
diff --git a/src/Antiforgery/ref/Microsoft.AspNetCore.Antiforgery.csproj b/src/Antiforgery/ref/Microsoft.AspNetCore.Antiforgery.csproj
index 451b80df95..ab33043f0c 100644
--- a/src/Antiforgery/ref/Microsoft.AspNetCore.Antiforgery.csproj
+++ b/src/Antiforgery/ref/Microsoft.AspNetCore.Antiforgery.csproj
@@ -2,6 +2,7 @@
 <Project Sdk="Microsoft.NET.Sdk">
   <PropertyGroup>
     <TargetFrameworks>$(DefaultNetCoreTargetFramework)</TargetFrameworks>
+    <Nullable>annotations</Nullable>
   </PropertyGroup>
   <ItemGroup Condition="'$(TargetFramework)' == '$(DefaultNetCoreTargetFramework)'">
     <Compile Include="Microsoft.AspNetCore.Antiforgery.netcoreapp.cs" />
diff --git a/src/Antiforgery/ref/Microsoft.AspNetCore.Antiforgery.netcoreapp.cs b/src/Antiforgery/ref/Microsoft.AspNetCore.Antiforgery.netcoreapp.cs
index 4ca6748cce..ca33981a59 100644
--- a/src/Antiforgery/ref/Microsoft.AspNetCore.Antiforgery.netcoreapp.cs
+++ b/src/Antiforgery/ref/Microsoft.AspNetCore.Antiforgery.netcoreapp.cs
@@ -9,21 +9,21 @@ namespace Microsoft.AspNetCore.Antiforgery
         public AntiforgeryOptions() { }
         public Microsoft.AspNetCore.Http.CookieBuilder Cookie { get { throw null; } set { } }
         public string FormFieldName { get { throw null; } set { } }
-        public string HeaderName { [System.Runtime.CompilerServices.CompilerGeneratedAttribute] get { throw null; } [System.Runtime.CompilerServices.CompilerGeneratedAttribute] set { } }
+        public string? HeaderName { [System.Runtime.CompilerServices.CompilerGeneratedAttribute] get { throw null; } [System.Runtime.CompilerServices.CompilerGeneratedAttribute] set { } }
         public bool SuppressXFrameOptionsHeader { [System.Runtime.CompilerServices.CompilerGeneratedAttribute] get { throw null; } [System.Runtime.CompilerServices.CompilerGeneratedAttribute] set { } }
     }
     public partial class AntiforgeryTokenSet
     {
-        public AntiforgeryTokenSet(string requestToken, string cookieToken, string formFieldName, string headerName) { }
-        public string CookieToken { [System.Runtime.CompilerServices.CompilerGeneratedAttribute] get { throw null; } }
+        public AntiforgeryTokenSet(string? requestToken, string? cookieToken, string formFieldName, string? headerName) { }
+        public string? CookieToken { [System.Runtime.CompilerServices.CompilerGeneratedAttribute] get { throw null; } }
         public string FormFieldName { [System.Runtime.CompilerServices.CompilerGeneratedAttribute] get { throw null; } }
-        public string HeaderName { [System.Runtime.CompilerServices.CompilerGeneratedAttribute] get { throw null; } }
-        public string RequestToken { [System.Runtime.CompilerServices.CompilerGeneratedAttribute] get { throw null; } }
+        public string? HeaderName { [System.Runtime.CompilerServices.CompilerGeneratedAttribute] get { throw null; } }
+        public string? RequestToken { [System.Runtime.CompilerServices.CompilerGeneratedAttribute] get { throw null; } }
     }
     public partial class AntiforgeryValidationException : System.Exception
     {
         public AntiforgeryValidationException(string message) { }
-        public AntiforgeryValidationException(string message, System.Exception innerException) { }
+        public AntiforgeryValidationException(string message, System.Exception? innerException) { }
     }
     public partial interface IAntiforgery
     {
diff --git a/src/Antiforgery/src/AntiforgeryOptions.cs b/src/Antiforgery/src/AntiforgeryOptions.cs
index 36906cf475..b7d50b22d6 100644
--- a/src/Antiforgery/src/AntiforgeryOptions.cs
+++ b/src/Antiforgery/src/AntiforgeryOptions.cs
@@ -73,7 +73,7 @@ namespace Microsoft.AspNetCore.Antiforgery
         /// Specifies the name of the header value that is used by the antiforgery system. If <c>null</c> then
         /// antiforgery validation will only consider form data.
         /// </summary>
-        public string HeaderName { get; set; } = AntiforgeryTokenHeaderName;
+        public string? HeaderName { get; set; } = AntiforgeryTokenHeaderName;
 
         /// <summary>
         /// Specifies whether to suppress the generation of X-Frame-Options header
diff --git a/src/Antiforgery/src/AntiforgeryTokenSet.cs b/src/Antiforgery/src/AntiforgeryTokenSet.cs
index 033e5e0731..5aa4669276 100644
--- a/src/Antiforgery/src/AntiforgeryTokenSet.cs
+++ b/src/Antiforgery/src/AntiforgeryTokenSet.cs
@@ -18,10 +18,10 @@ namespace Microsoft.AspNetCore.Antiforgery
         /// <param name="formFieldName">The name of the form field used for the request token.</param>
         /// <param name="headerName">The name of the header used for the request token.</param>
         public AntiforgeryTokenSet(
-            string requestToken,
-            string cookieToken,
+            string? requestToken,
+            string? cookieToken,
             string formFieldName,
-            string headerName)
+            string? headerName)
         {
             if (formFieldName == null)
             {
@@ -37,7 +37,7 @@ namespace Microsoft.AspNetCore.Antiforgery
         /// <summary>
         /// Gets the request token.
         /// </summary>
-        public string RequestToken { get; }
+        public string? RequestToken { get; }
 
         /// <summary>
         /// Gets the name of the form field used for the request token.
@@ -47,11 +47,11 @@ namespace Microsoft.AspNetCore.Antiforgery
         /// <summary>
         /// Gets the name of the header used for the request token.
         /// </summary>
-        public string HeaderName { get; }
+        public string? HeaderName { get; }
 
         /// <summary>
         /// Gets the cookie token.
         /// </summary>
-        public string CookieToken { get; }
+        public string? CookieToken { get; }
     }
-}
\ No newline at end of file
+}
diff --git a/src/Antiforgery/src/AntiforgeryValidationException.cs b/src/Antiforgery/src/AntiforgeryValidationException.cs
index f1ade05d34..700c13f34b 100644
--- a/src/Antiforgery/src/AntiforgeryValidationException.cs
+++ b/src/Antiforgery/src/AntiforgeryValidationException.cs
@@ -26,7 +26,7 @@ namespace Microsoft.AspNetCore.Antiforgery
         /// </summary>
         /// <param name="message">The message that describes the error.</param>
         /// <param name="innerException">The inner <see cref="Exception"/>.</param>
-        public AntiforgeryValidationException(string message, Exception innerException)
+        public AntiforgeryValidationException(string message, Exception? innerException)
             : base(message, innerException)
         {
         }
diff --git a/src/Antiforgery/src/Internal/AntiforgeryFeature.cs b/src/Antiforgery/src/Internal/AntiforgeryFeature.cs
index 632c835df8..5d65e8ac70 100644
--- a/src/Antiforgery/src/Internal/AntiforgeryFeature.cs
+++ b/src/Antiforgery/src/Internal/AntiforgeryFeature.cs
@@ -10,23 +10,23 @@ namespace Microsoft.AspNetCore.Antiforgery
     {
         public bool HaveDeserializedCookieToken { get; set; }
 
-        public AntiforgeryToken CookieToken { get; set; }
+        public AntiforgeryToken? CookieToken { get; set; }
 
         public bool HaveDeserializedRequestToken { get; set; }
 
-        public AntiforgeryToken RequestToken { get; set; }
+        public AntiforgeryToken? RequestToken { get; set; }
 
         public bool HaveGeneratedNewCookieToken { get; set; }
 
         // After HaveGeneratedNewCookieToken is true, remains null if CookieToken is valid.
-        public AntiforgeryToken NewCookieToken { get; set; }
+        public AntiforgeryToken? NewCookieToken { get; set; }
 
         // After HaveGeneratedNewCookieToken is true, remains null if CookieToken is valid.
-        public string NewCookieTokenString { get; set; }
+        public string? NewCookieTokenString { get; set; }
 
-        public AntiforgeryToken NewRequestToken { get; set; }
+        public AntiforgeryToken? NewRequestToken { get; set; }
 
-        public string NewRequestTokenString { get; set; }
+        public string? NewRequestTokenString { get; set; }
 
         // Always false if NewCookieToken is null. Never store null cookie token or re-store cookie token from request.
         public bool HaveStoredNewCookieToken { get; set; }
diff --git a/src/Antiforgery/src/Internal/AntiforgeryLoggerExtensions.cs b/src/Antiforgery/src/Internal/AntiforgeryLoggerExtensions.cs
index 6bc7e60cd5..7c5b1d49e7 100644
--- a/src/Antiforgery/src/Internal/AntiforgeryLoggerExtensions.cs
+++ b/src/Antiforgery/src/Internal/AntiforgeryLoggerExtensions.cs
@@ -8,15 +8,15 @@ namespace Microsoft.AspNetCore.Antiforgery
 {
     internal static class AntiforgeryLoggerExtensions
     {
-        private static readonly Action<ILogger, Exception> _failedToDeserialzeTokens;
-        private static readonly Action<ILogger, string, Exception> _validationFailed;
-        private static readonly Action<ILogger, Exception> _validated;
-        private static readonly Action<ILogger, string, Exception> _missingCookieToken;
-        private static readonly Action<ILogger, string, string, Exception> _missingRequestToken;
-        private static readonly Action<ILogger, Exception> _newCookieToken;
-        private static readonly Action<ILogger, Exception> _reusedCookieToken;
-        private static readonly Action<ILogger, Exception> _tokenDeserializeException;
-        private static readonly Action<ILogger, Exception> _responseCacheHeadersOverridenToNoCache;
+        private static readonly Action<ILogger, Exception?> _failedToDeserialzeTokens;
+        private static readonly Action<ILogger, string, Exception?> _validationFailed;
+        private static readonly Action<ILogger, Exception?> _validated;
+        private static readonly Action<ILogger, string?, Exception?> _missingCookieToken;
+        private static readonly Action<ILogger, string, string?, Exception?> _missingRequestToken;
+        private static readonly Action<ILogger, Exception?> _newCookieToken;
+        private static readonly Action<ILogger, Exception?> _reusedCookieToken;
+        private static readonly Action<ILogger, Exception?> _tokenDeserializeException;
+        private static readonly Action<ILogger, Exception?> _responseCacheHeadersOverridenToNoCache;
 
         static AntiforgeryLoggerExtensions()
         {
@@ -28,11 +28,11 @@ namespace Microsoft.AspNetCore.Antiforgery
                 LogLevel.Debug,
                 new EventId(2, "Validated"),
                 "Antiforgery successfully validated a request.");
-            _missingCookieToken = LoggerMessage.Define<string>(
+            _missingCookieToken = LoggerMessage.Define<string?>(
                 LogLevel.Warning,
                 new EventId(3, "MissingCookieToken"),
                 "The required antiforgery cookie '{CookieName}' is not present.");
-            _missingRequestToken = LoggerMessage.Define<string, string>(
+            _missingRequestToken = LoggerMessage.Define<string, string?>(
                 LogLevel.Warning,
                 new EventId(4, "MissingRequestToken"),
                 "The required antiforgery request token was not provided in either form field '{FormFieldName}' "
@@ -71,12 +71,12 @@ namespace Microsoft.AspNetCore.Antiforgery
             _validated(logger, null);
         }
 
-        public static void MissingCookieToken(this ILogger logger, string cookieName)
+        public static void MissingCookieToken(this ILogger logger, string? cookieName)
         {
             _missingCookieToken(logger, cookieName, null);
         }
 
-        public static void MissingRequestToken(this ILogger logger, string formFieldName, string headerName)
+        public static void MissingRequestToken(this ILogger logger, string formFieldName, string? headerName)
         {
             _missingRequestToken(logger, formFieldName, headerName, null);
         }
diff --git a/src/Antiforgery/src/Internal/AntiforgerySerializationContext.cs b/src/Antiforgery/src/Internal/AntiforgerySerializationContext.cs
index 87fe89d49c..342d1d8fb4 100644
--- a/src/Antiforgery/src/Internal/AntiforgerySerializationContext.cs
+++ b/src/Antiforgery/src/Internal/AntiforgerySerializationContext.cs
@@ -23,11 +23,11 @@ namespace Microsoft.AspNetCore.Antiforgery
         // Don't let _chars grow beyond 512k characters.
         private const int MaximumCharsLength = 0x80000;
 
-        private char[] _chars;
-        private MemoryStream _stream;
-        private BinaryReader _reader;
-        private BinaryWriter _writer;
-        private SHA256 _sha256;
+        private char[]? _chars;
+        private MemoryStream? _stream;
+        private BinaryReader? _reader;
+        private BinaryWriter? _writer;
+        private SHA256? _sha256;
 
         public MemoryStream Stream
         {
@@ -126,9 +126,9 @@ namespace Microsoft.AspNetCore.Antiforgery
             {
                 if (Stream.Capacity > MaximumStreamSize)
                 {
-                    Stream = null;
-                    Reader = null;
-                    Writer = null;
+                    _stream = null;
+                    _reader = null;
+                    _writer = null;
                 }
                 else
                 {
diff --git a/src/Antiforgery/src/Internal/AntiforgeryToken.cs b/src/Antiforgery/src/Internal/AntiforgeryToken.cs
index 59e9b83e5a..590f92f554 100644
--- a/src/Antiforgery/src/Internal/AntiforgeryToken.cs
+++ b/src/Antiforgery/src/Internal/AntiforgeryToken.cs
@@ -10,7 +10,7 @@ namespace Microsoft.AspNetCore.Antiforgery
 
         private string _additionalData = string.Empty;
         private string _username = string.Empty;
-        private BinaryBlob _securityToken;
+        private BinaryBlob? _securityToken;
 
         public string AdditionalData
         {
@@ -21,11 +21,11 @@ namespace Microsoft.AspNetCore.Antiforgery
             }
         }
 
-        public BinaryBlob ClaimUid { get; set; }
+        public BinaryBlob? ClaimUid { get; set; }
 
         public bool IsCookieToken { get; set; }
 
-        public BinaryBlob SecurityToken
+        public BinaryBlob? SecurityToken
         {
             get
             {
@@ -41,7 +41,7 @@ namespace Microsoft.AspNetCore.Antiforgery
             }
         }
 
-        public string Username
+        public string? Username
         {
             get { return _username; }
             set
diff --git a/src/Antiforgery/src/Internal/BinaryBlob.cs b/src/Antiforgery/src/Internal/BinaryBlob.cs
index 9313175b36..a33f727bd4 100644
--- a/src/Antiforgery/src/Internal/BinaryBlob.cs
+++ b/src/Antiforgery/src/Internal/BinaryBlob.cs
@@ -59,12 +59,12 @@ namespace Microsoft.AspNetCore.Antiforgery
             }
         }
 
-        public override bool Equals(object obj)
+        public override bool Equals(object? obj)
         {
             return Equals(obj as BinaryBlob);
         }
 
-        public bool Equals(BinaryBlob other)
+        public bool Equals(BinaryBlob? other)
         {
             if (other == null)
             {
diff --git a/src/Antiforgery/src/Internal/DefaultAntiforgery.cs b/src/Antiforgery/src/Internal/DefaultAntiforgery.cs
index f88d18bf8a..b310d2286b 100644
--- a/src/Antiforgery/src/Internal/DefaultAntiforgery.cs
+++ b/src/Antiforgery/src/Internal/DefaultAntiforgery.cs
@@ -3,6 +3,7 @@
 
 using System;
 using System.Diagnostics;
+using System.Diagnostics.CodeAnalysis;
 using System.Threading.Tasks;
 using Microsoft.AspNetCore.Http;
 using Microsoft.Extensions.Logging;
@@ -125,9 +126,7 @@ namespace Microsoft.AspNetCore.Antiforgery
             }
 
             // Extract cookie & request tokens
-            AntiforgeryToken deserializedCookieToken;
-            AntiforgeryToken deserializedRequestToken;
-            if (!TryDeserializeTokens(httpContext, tokens, out deserializedCookieToken, out deserializedRequestToken))
+            if (!TryDeserializeTokens(httpContext, tokens, out var deserializedCookieToken, out var deserializedRequestToken))
             {
                 return false;
             }
@@ -137,7 +136,7 @@ namespace Microsoft.AspNetCore.Antiforgery
                 httpContext,
                 deserializedCookieToken,
                 deserializedRequestToken,
-                out string message);
+                out var message);
 
             if (result)
             {
@@ -145,7 +144,7 @@ namespace Microsoft.AspNetCore.Antiforgery
             }
             else
             {
-                _logger.ValidationFailed(message);
+                _logger.ValidationFailed(message!);
             }
 
             return result;
@@ -210,12 +209,11 @@ namespace Microsoft.AspNetCore.Antiforgery
                 out deserializedRequestToken);
 
             // Validate
-            string message;
             if (!_tokenGenerator.TryValidateTokenSet(
                 httpContext,
                 deserializedCookieToken,
                 deserializedRequestToken,
-                out message))
+                out var message))
             {
                 throw new AntiforgeryValidationException(message);
             }
@@ -306,7 +304,7 @@ namespace Microsoft.AspNetCore.Antiforgery
                 return antiforgeryFeature;
             }
 
-            AntiforgeryToken cookieToken;
+            AntiforgeryToken? cookieToken;
             if (antiforgeryFeature.HaveDeserializedCookieToken)
             {
                 cookieToken = antiforgeryFeature.CookieToken;
@@ -319,7 +317,7 @@ namespace Microsoft.AspNetCore.Antiforgery
                 antiforgeryFeature.HaveDeserializedCookieToken = true;
             }
 
-            AntiforgeryToken newCookieToken;
+            AntiforgeryToken? newCookieToken;
             if (_tokenGenerator.IsCookieTokenValid(cookieToken))
             {
                 // No need for the cookie token from the request after it has been verified.
@@ -338,7 +336,7 @@ namespace Microsoft.AspNetCore.Antiforgery
             return antiforgeryFeature;
         }
 
-        private AntiforgeryToken GetCookieTokenDoesNotThrow(HttpContext httpContext)
+        private AntiforgeryToken? GetCookieTokenDoesNotThrow(HttpContext httpContext)
         {
             try
             {
@@ -367,7 +365,7 @@ namespace Microsoft.AspNetCore.Antiforgery
                 var cookieToken = antiforgeryFeature.NewCookieToken ?? antiforgeryFeature.CookieToken;
                 antiforgeryFeature.NewRequestToken = _tokenGenerator.GenerateRequestToken(
                     httpContext,
-                    cookieToken);
+                    cookieToken!);
             }
 
             return antiforgeryFeature;
@@ -391,8 +389,7 @@ namespace Microsoft.AspNetCore.Antiforgery
         private void LogCacheHeaderOverrideWarning(HttpResponse response)
         {
             var logWarning = false;
-            CacheControlHeaderValue cacheControlHeaderValue;
-            if (CacheControlHeaderValue.TryParse(response.Headers[HeaderNames.CacheControl].ToString(), out cacheControlHeaderValue))
+            if (CacheControlHeaderValue.TryParse(response.Headers[HeaderNames.CacheControl].ToString(), out var cacheControlHeaderValue))
             {
                 if (!cacheControlHeaderValue.NoCache)
                 {
@@ -434,7 +431,7 @@ namespace Microsoft.AspNetCore.Antiforgery
 
             return new AntiforgeryTokenSet(
                 antiforgeryFeature.NewRequestTokenString,
-                antiforgeryFeature.NewCookieTokenString,
+                antiforgeryFeature.NewCookieTokenString!,
                 _options.FormFieldName,
                 _options.HeaderName);
         }
@@ -442,8 +439,8 @@ namespace Microsoft.AspNetCore.Antiforgery
         private bool TryDeserializeTokens(
             HttpContext httpContext,
             AntiforgeryTokenSet antiforgeryTokenSet,
-            out AntiforgeryToken cookieToken,
-            out AntiforgeryToken requestToken)
+            [NotNullWhen(true)] out AntiforgeryToken? cookieToken,
+            [NotNullWhen(true)] out AntiforgeryToken? requestToken)
         {
             try
             {
@@ -470,11 +467,11 @@ namespace Microsoft.AspNetCore.Antiforgery
 
             if (antiforgeryFeature.HaveDeserializedCookieToken)
             {
-                cookieToken = antiforgeryFeature.CookieToken;
+                cookieToken = antiforgeryFeature.CookieToken!;
             }
             else
             {
-                cookieToken = _tokenSerializer.Deserialize(antiforgeryTokenSet.CookieToken);
+                cookieToken = _tokenSerializer.Deserialize(antiforgeryTokenSet.CookieToken!);
 
                 antiforgeryFeature.CookieToken = cookieToken;
                 antiforgeryFeature.HaveDeserializedCookieToken = true;
@@ -482,11 +479,11 @@ namespace Microsoft.AspNetCore.Antiforgery
 
             if (antiforgeryFeature.HaveDeserializedRequestToken)
             {
-                requestToken = antiforgeryFeature.RequestToken;
+                requestToken = antiforgeryFeature.RequestToken!;
             }
             else
             {
-                requestToken = _tokenSerializer.Deserialize(antiforgeryTokenSet.RequestToken);
+                requestToken = _tokenSerializer.Deserialize(antiforgeryTokenSet.RequestToken!);
 
                 antiforgeryFeature.RequestToken = requestToken;
                 antiforgeryFeature.HaveDeserializedRequestToken = true;
diff --git a/src/Antiforgery/src/Internal/DefaultAntiforgeryTokenGenerator.cs b/src/Antiforgery/src/Internal/DefaultAntiforgeryTokenGenerator.cs
index 03994ec1e9..62230190bc 100644
--- a/src/Antiforgery/src/Internal/DefaultAntiforgeryTokenGenerator.cs
+++ b/src/Antiforgery/src/Internal/DefaultAntiforgeryTokenGenerator.cs
@@ -3,6 +3,7 @@
 
 using System;
 using System.Collections.Generic;
+using System.Diagnostics.CodeAnalysis;
 using System.Security.Claims;
 using System.Security.Principal;
 using Microsoft.AspNetCore.Http;
@@ -89,7 +90,7 @@ namespace Microsoft.AspNetCore.Antiforgery
                 // Application says user is authenticated, but we have no identifier for the user.
                 throw new InvalidOperationException(
                     Resources.FormatAntiforgeryTokenValidator_AuthenticatedUserWithoutUsername(
-                        authenticatedIdentity.GetType(),
+                        authenticatedIdentity?.GetType() ?? typeof(ClaimsIdentity),
                         nameof(IIdentity.IsAuthenticated),
                         "true",
                         nameof(IIdentity.Name),
@@ -101,7 +102,7 @@ namespace Microsoft.AspNetCore.Antiforgery
         }
 
         /// <inheritdoc />
-        public bool IsCookieTokenValid(AntiforgeryToken cookieToken)
+        public bool IsCookieTokenValid(AntiforgeryToken? cookieToken)
         {
             return cookieToken != null && cookieToken.IsCookieToken;
         }
@@ -111,7 +112,7 @@ namespace Microsoft.AspNetCore.Antiforgery
             HttpContext httpContext,
             AntiforgeryToken cookieToken,
             AntiforgeryToken requestToken,
-            out string message)
+            [NotNullWhen(false)] out string? message)
         {
             if (httpContext == null)
             {
@@ -148,7 +149,7 @@ namespace Microsoft.AspNetCore.Antiforgery
 
             // Is the incoming token meant for the current user?
             var currentUsername = string.Empty;
-            BinaryBlob currentClaimUid = null;
+            BinaryBlob? currentClaimUid = null;
 
             var authenticatedIdentity = GetAuthenticatedIdentity(httpContext.User);
             if (authenticatedIdentity != null)
@@ -193,7 +194,7 @@ namespace Microsoft.AspNetCore.Antiforgery
             return true;
         }
 
-        private static BinaryBlob GetClaimUidBlob(string base64ClaimUid)
+        private static BinaryBlob? GetClaimUidBlob(string? base64ClaimUid)
         {
             if (base64ClaimUid == null)
             {
@@ -203,7 +204,7 @@ namespace Microsoft.AspNetCore.Antiforgery
             return new BinaryBlob(256, Convert.FromBase64String(base64ClaimUid));
         }
 
-        private static ClaimsIdentity GetAuthenticatedIdentity(ClaimsPrincipal claimsPrincipal)
+        private static ClaimsIdentity? GetAuthenticatedIdentity(ClaimsPrincipal? claimsPrincipal)
         {
             if (claimsPrincipal == null)
             {
diff --git a/src/Antiforgery/src/Internal/DefaultAntiforgeryTokenSerializer.cs b/src/Antiforgery/src/Internal/DefaultAntiforgeryTokenSerializer.cs
index 73a0e0ad63..fff8aa9175 100644
--- a/src/Antiforgery/src/Internal/DefaultAntiforgeryTokenSerializer.cs
+++ b/src/Antiforgery/src/Internal/DefaultAntiforgeryTokenSerializer.cs
@@ -39,7 +39,7 @@ namespace Microsoft.AspNetCore.Antiforgery
         {
             var serializationContext = _pool.Get();
 
-            Exception innerException = null;
+            Exception? innerException = null;
             try
             {
                 var count = serializedToken.Length;
@@ -90,7 +90,7 @@ namespace Microsoft.AspNetCore.Antiforgery
          *   |    `- Username: UTF-8 string with 7-bit integer length prefix
          *   `- AdditionalData: UTF-8 string with 7-bit integer length prefix
          */
-        private static AntiforgeryToken Deserialize(BinaryReader reader)
+        private static AntiforgeryToken? Deserialize(BinaryReader reader)
         {
             // we can only consume tokens of the same serialized version that we generate
             var embeddedVersion = reader.ReadByte();
@@ -144,7 +144,7 @@ namespace Microsoft.AspNetCore.Antiforgery
             {
                 var writer = serializationContext.Writer;
                 writer.Write(TokenVersion);
-                writer.Write(token.SecurityToken.GetData());
+                writer.Write(token.SecurityToken!.GetData());
                 writer.Write(token.IsCookieToken);
 
                 if (!token.IsCookieToken)
@@ -157,7 +157,7 @@ namespace Microsoft.AspNetCore.Antiforgery
                     else
                     {
                         writer.Write(false /* isClaimsBased */);
-                        writer.Write(token.Username);
+                        writer.Write(token.Username!);
                     }
 
                     writer.Write(token.AdditionalData);
diff --git a/src/Antiforgery/src/Internal/DefaultAntiforgeryTokenStore.cs b/src/Antiforgery/src/Internal/DefaultAntiforgeryTokenStore.cs
index e30fe0df4d..b35358fea2 100644
--- a/src/Antiforgery/src/Internal/DefaultAntiforgeryTokenStore.cs
+++ b/src/Antiforgery/src/Internal/DefaultAntiforgeryTokenStore.cs
@@ -24,11 +24,11 @@ namespace Microsoft.AspNetCore.Antiforgery
             _options = optionsAccessor.Value;
         }
 
-        public string GetCookieToken(HttpContext httpContext)
+        public string? GetCookieToken(HttpContext httpContext)
         {
             Debug.Assert(httpContext != null);
 
-            var requestCookie = httpContext.Request.Cookies[_options.Cookie.Name];
+            var requestCookie = httpContext.Request.Cookies[_options.Cookie.Name!];
             if (string.IsNullOrEmpty(requestCookie))
             {
                 // unable to find the cookie.
@@ -42,7 +42,7 @@ namespace Microsoft.AspNetCore.Antiforgery
         {
             Debug.Assert(httpContext != null);
 
-            var cookieToken = httpContext.Request.Cookies[_options.Cookie.Name];
+            var cookieToken = httpContext.Request.Cookies[_options.Cookie.Name!];
 
             // We want to delay reading the form as much as possible, for example in case of large file uploads,
             // request token could be part of the header.
@@ -84,7 +84,7 @@ namespace Microsoft.AspNetCore.Antiforgery
                 }
             }
 
-            httpContext.Response.Cookies.Append(_options.Cookie.Name, token, options);
+            httpContext.Response.Cookies.Append(_options.Cookie.Name!, token, options);
         }
     }
 }
diff --git a/src/Antiforgery/src/Internal/DefaultClaimUidExtractor.cs b/src/Antiforgery/src/Internal/DefaultClaimUidExtractor.cs
index fb4d386516..3df55b523f 100644
--- a/src/Antiforgery/src/Internal/DefaultClaimUidExtractor.cs
+++ b/src/Antiforgery/src/Internal/DefaultClaimUidExtractor.cs
@@ -22,7 +22,7 @@ namespace Microsoft.AspNetCore.Antiforgery
         }
 
         /// <inheritdoc />
-        public string ExtractClaimUid(ClaimsPrincipal claimsPrincipal)
+        public string? ExtractClaimUid(ClaimsPrincipal claimsPrincipal)
         {
             Debug.Assert(claimsPrincipal != null);
 
@@ -37,7 +37,7 @@ namespace Microsoft.AspNetCore.Antiforgery
             return Convert.ToBase64String(claimUidBytes);
         }
 
-        public static IList<string> GetUniqueIdentifierParameters(IEnumerable<ClaimsIdentity> claimsIdentities)
+        public static IList<string>? GetUniqueIdentifierParameters(IEnumerable<ClaimsIdentity> claimsIdentities)
         {
             var identitiesList = claimsIdentities as List<ClaimsIdentity>;
             if (identitiesList == null)
diff --git a/src/Antiforgery/src/Internal/IAntiforgeryFeature.cs b/src/Antiforgery/src/Internal/IAntiforgeryFeature.cs
index c96db16708..c73c33f1aa 100644
--- a/src/Antiforgery/src/Internal/IAntiforgeryFeature.cs
+++ b/src/Antiforgery/src/Internal/IAntiforgeryFeature.cs
@@ -1,8 +1,10 @@
+using System.Diagnostics.CodeAnalysis;
+
 namespace Microsoft.AspNetCore.Antiforgery
 {
     internal interface IAntiforgeryFeature
     {
-        AntiforgeryToken CookieToken { get; set; }
+        AntiforgeryToken? CookieToken { get; set; }
 
         bool HaveDeserializedCookieToken { get; set; }
 
@@ -12,14 +14,14 @@ namespace Microsoft.AspNetCore.Antiforgery
 
         bool HaveStoredNewCookieToken { get; set; }
 
-        AntiforgeryToken NewCookieToken { get; set; }
+        AntiforgeryToken? NewCookieToken { get; set; }
 
-        string NewCookieTokenString { get; set; }
+        string? NewCookieTokenString { get; set; }
 
-        AntiforgeryToken NewRequestToken { get; set; }
+        AntiforgeryToken? NewRequestToken { get; set; }
 
-        string NewRequestTokenString { get; set; }
+        string? NewRequestTokenString { get; set; }
 
-        AntiforgeryToken RequestToken { get; set; }
+        AntiforgeryToken? RequestToken { get; set; }
     }
 }
diff --git a/src/Antiforgery/src/Internal/IAntiforgeryTokenGenerator.cs b/src/Antiforgery/src/Internal/IAntiforgeryTokenGenerator.cs
index 59cb3118cd..b3629ff468 100644
--- a/src/Antiforgery/src/Internal/IAntiforgeryTokenGenerator.cs
+++ b/src/Antiforgery/src/Internal/IAntiforgeryTokenGenerator.cs
@@ -1,6 +1,7 @@
 // Copyright (c) .NET Foundation. All rights reserved.
 // Licensed under the Apache License, Version 2.0. See License.txt in the project root for license information.
 
+using System.Diagnostics.CodeAnalysis;
 using Microsoft.AspNetCore.Http;
 
 namespace Microsoft.AspNetCore.Antiforgery
@@ -29,7 +30,7 @@ namespace Microsoft.AspNetCore.Antiforgery
         /// </summary>
         /// <param name="cookieToken">A valid cookie token.</param>
         /// <returns><c>true</c> if the cookie token is valid, otherwise <c>false</c>.</returns>
-        bool IsCookieTokenValid(AntiforgeryToken cookieToken);
+        bool IsCookieTokenValid(AntiforgeryToken? cookieToken);
 
         /// <summary>
         /// Attempts to validate a cookie and request token set for the given <paramref name="httpContext"/>.
@@ -45,6 +46,6 @@ namespace Microsoft.AspNetCore.Antiforgery
             HttpContext httpContext,
             AntiforgeryToken cookieToken,
             AntiforgeryToken requestToken,
-            out string message);
+            [NotNullWhen(false)] out string? message);
     }
 }
diff --git a/src/Antiforgery/src/Internal/IAntiforgeryTokenStore.cs b/src/Antiforgery/src/Internal/IAntiforgeryTokenStore.cs
index dd3f29e835..f202e90f5e 100644
--- a/src/Antiforgery/src/Internal/IAntiforgeryTokenStore.cs
+++ b/src/Antiforgery/src/Internal/IAntiforgeryTokenStore.cs
@@ -8,7 +8,7 @@ namespace Microsoft.AspNetCore.Antiforgery
 {
     internal interface IAntiforgeryTokenStore
     {
-        string GetCookieToken(HttpContext httpContext);
+        string? GetCookieToken(HttpContext httpContext);
 
         /// <summary>
         /// Gets the cookie and request tokens from the request.
diff --git a/src/Antiforgery/src/Internal/IClaimUidExtractor.cs b/src/Antiforgery/src/Internal/IClaimUidExtractor.cs
index 29d264789d..0153e10bc7 100644
--- a/src/Antiforgery/src/Internal/IClaimUidExtractor.cs
+++ b/src/Antiforgery/src/Internal/IClaimUidExtractor.cs
@@ -15,6 +15,6 @@ namespace Microsoft.AspNetCore.Antiforgery
         /// </summary>
         /// <param name="claimsPrincipal">The <see cref="ClaimsPrincipal"/>.</param>
         /// <returns>The claims identifier.</returns>
-        string ExtractClaimUid(ClaimsPrincipal claimsPrincipal);
+        string? ExtractClaimUid(ClaimsPrincipal claimsPrincipal);
     }
 }
diff --git a/src/Antiforgery/src/Microsoft.AspNetCore.Antiforgery.csproj b/src/Antiforgery/src/Microsoft.AspNetCore.Antiforgery.csproj
index 566e221871..4723a65cec 100644
--- a/src/Antiforgery/src/Microsoft.AspNetCore.Antiforgery.csproj
+++ b/src/Antiforgery/src/Microsoft.AspNetCore.Antiforgery.csproj
@@ -7,6 +7,7 @@
     <GenerateDocumentationFile>true</GenerateDocumentationFile>
     <PackageTags>aspnetcore;antiforgery</PackageTags>
     <IsPackable>false</IsPackable>
+    <Nullable>enable</Nullable>
   </PropertyGroup>
 
   <ItemGroup>
diff --git a/src/Antiforgery/test/AntiforgeryTokenTest.cs b/src/Antiforgery/test/AntiforgeryTokenTest.cs
index 9cafd306b0..c44f5be575 100644
--- a/src/Antiforgery/test/AntiforgeryTokenTest.cs
+++ b/src/Antiforgery/test/AntiforgeryTokenTest.cs
@@ -21,7 +21,7 @@ namespace Microsoft.AspNetCore.Antiforgery.Internal
             Assert.Equal("additional data", token.AdditionalData);
 
             // Act & assert - 3
-            token.AdditionalData = null;
+            token.AdditionalData = null!;
             Assert.Equal("", token.AdditionalData);
         }
 
@@ -91,7 +91,7 @@ namespace Microsoft.AspNetCore.Antiforgery.Internal
 
             // Assert
             Assert.NotNull(securityToken);
-            Assert.Equal(AntiforgeryToken.SecurityTokenBitLength, securityToken.BitLength);
+            Assert.Equal(AntiforgeryToken.SecurityTokenBitLength, securityToken!.BitLength);
 
             // check that we're not making a new one each property call
             Assert.Equal(securityToken, token.SecurityToken);
@@ -123,10 +123,10 @@ namespace Microsoft.AspNetCore.Antiforgery.Internal
 
             // Assert
             Assert.NotNull(securityToken);
-            Assert.Equal(AntiforgeryToken.SecurityTokenBitLength, securityToken.BitLength);
+            Assert.Equal(AntiforgeryToken.SecurityTokenBitLength, securityToken!.BitLength);
 
             // check that we're not making a new one each property call
             Assert.Equal(securityToken, token.SecurityToken);
         }
     }
-}
\ No newline at end of file
+}
diff --git a/src/Antiforgery/test/BinaryBlobTest.cs b/src/Antiforgery/test/BinaryBlobTest.cs
index 2ab5b12fc1..01c77ff684 100644
--- a/src/Antiforgery/test/BinaryBlobTest.cs
+++ b/src/Antiforgery/test/BinaryBlobTest.cs
@@ -57,7 +57,7 @@ namespace Microsoft.AspNetCore.Antiforgery.Internal
         }
 
         [Theory]
-        [InlineData((object[])null)]
+        [InlineData((object[]?)null)]
         [InlineData(new byte[] { 0x01, 0x02, 0x03 })]
         public void Ctor_Data_Bad(byte[] data)
         {
@@ -93,7 +93,7 @@ namespace Microsoft.AspNetCore.Antiforgery.Internal
         {
             // Arrange
             object blobA = new BinaryBlob(32);
-            object blobB = null;
+            object? blobB = null;
 
             // Act & assert
             Assert.NotEqual(blobA, blobB);
@@ -126,4 +126,4 @@ namespace Microsoft.AspNetCore.Antiforgery.Internal
             Assert.Equal(expectedHashCode, actualHashCode);
         }
     }
-}
\ No newline at end of file
+}
diff --git a/src/Antiforgery/test/DefaultAntiforgeryTest.cs b/src/Antiforgery/test/DefaultAntiforgeryTest.cs
index 63ee690f35..048efea215 100644
--- a/src/Antiforgery/test/DefaultAntiforgeryTest.cs
+++ b/src/Antiforgery/test/DefaultAntiforgeryTest.cs
@@ -509,7 +509,7 @@ namespace Microsoft.AspNetCore.Antiforgery.Internal
             var antiforgeryFeature = new AntiforgeryFeature();
             var context = CreateMockContext(new AntiforgeryOptions(), antiforgeryFeature: antiforgeryFeature);
 
-            string message;
+            string? message;
             context.TokenGenerator
                 .Setup(o => o.TryValidateTokenSet(
                     context.HttpContext,
@@ -543,7 +543,7 @@ namespace Microsoft.AspNetCore.Antiforgery.Internal
             var context = CreateMockContext(new AntiforgeryOptions(), antiforgeryFeature: antiforgeryFeature);
             context.HttpContext.Request.Method = "POST";
 
-            string message;
+            string? message;
             context.TokenGenerator
                 .Setup(o => o.TryValidateTokenSet(
                     context.HttpContext,
@@ -583,7 +583,7 @@ namespace Microsoft.AspNetCore.Antiforgery.Internal
             var context = CreateMockContext(new AntiforgeryOptions(), antiforgeryFeature: antiforgeryFeature);
             context.HttpContext.Request.Method = "POST";
 
-            string message;
+            string? message;
             context.TokenGenerator
                 .Setup(o => o.TryValidateTokenSet(
                     context.HttpContext,
@@ -622,7 +622,7 @@ namespace Microsoft.AspNetCore.Antiforgery.Internal
             var context = CreateMockContext(new AntiforgeryOptions());
             context.HttpContext.Request.Method = httpMethod;
 
-            string message;
+            string? message;
             context.TokenGenerator
                 .Setup(o => o.TryValidateTokenSet(
                     context.HttpContext,
@@ -659,7 +659,7 @@ namespace Microsoft.AspNetCore.Antiforgery.Internal
             var context = CreateMockContext(new AntiforgeryOptions());
             context.HttpContext.Request.Method = httpMethod;
 
-            string message;
+            string? message;
             context.TokenGenerator
                 .Setup(o => o.TryValidateTokenSet(
                     context.HttpContext,
@@ -718,7 +718,7 @@ namespace Microsoft.AspNetCore.Antiforgery.Internal
             var antiforgeryFeature = new AntiforgeryFeature();
             var context = CreateMockContext(new AntiforgeryOptions(), antiforgeryFeature: antiforgeryFeature);
 
-            string message;
+            string? message;
             context.TokenGenerator
                 .Setup(o => o.TryValidateTokenSet(
                     context.HttpContext,
@@ -859,7 +859,7 @@ namespace Microsoft.AspNetCore.Antiforgery.Internal
             };
             var context = CreateMockContext(new AntiforgeryOptions(), antiforgeryFeature: antiforgeryFeature);
 
-            string message;
+            string? message;
             context.TokenGenerator
                 .Setup(o => o.TryValidateTokenSet(
                     context.HttpContext,
@@ -1122,7 +1122,7 @@ namespace Microsoft.AspNetCore.Antiforgery.Internal
                 antiforgeryFeature: antiforgeryFeature);
             var testTokenSet = new TestTokenSet
             {
-                OldCookieTokenString = null
+                OldCookieTokenString = null!
             };
 
             var nullTokenStore = GetTokenStore(context.HttpContext, testTokenSet, false);
@@ -1135,7 +1135,7 @@ namespace Microsoft.AspNetCore.Antiforgery.Internal
             antiforgery.SetCookieTokenAndHeader(context.HttpContext);
 
             // Assert
-            context.TokenSerializer.Verify(s => s.Deserialize(null), Times.Never);
+            context.TokenSerializer.Verify(s => s.Deserialize(null!), Times.Never);
         }
 
         [Fact]
@@ -1159,7 +1159,7 @@ namespace Microsoft.AspNetCore.Antiforgery.Internal
                 antiforgeryFeature: antiforgeryFeature);
             var testTokenSet = new TestTokenSet
             {
-                OldCookieTokenString = null
+                OldCookieTokenString = null!
             };
 
             var nullTokenStore = GetTokenStore(context.HttpContext, testTokenSet, false);
@@ -1285,10 +1285,10 @@ namespace Microsoft.AspNetCore.Antiforgery.Internal
 
         private DefaultAntiforgery GetAntiforgery(
             HttpContext httpContext,
-            AntiforgeryOptions options = null,
-            IAntiforgeryTokenGenerator tokenGenerator = null,
-            IAntiforgeryTokenSerializer tokenSerializer = null,
-            IAntiforgeryTokenStore tokenStore = null)
+            AntiforgeryOptions? options = null,
+            IAntiforgeryTokenGenerator? tokenGenerator = null,
+            IAntiforgeryTokenSerializer? tokenSerializer = null,
+            IAntiforgeryTokenStore? tokenStore = null)
         {
             var optionsManager = new TestOptionsManager();
             if (options != null)
@@ -1299,9 +1299,9 @@ namespace Microsoft.AspNetCore.Antiforgery.Internal
             var loggerFactory = httpContext.RequestServices.GetRequiredService<ILoggerFactory>();
             return new DefaultAntiforgery(
                 antiforgeryOptionsAccessor: optionsManager,
-                tokenGenerator: tokenGenerator,
-                tokenSerializer: tokenSerializer,
-                tokenStore: tokenStore,
+                tokenGenerator: tokenGenerator!,
+                tokenSerializer: tokenSerializer!,
+                tokenStore: tokenStore!,
                 loggerFactory: loggerFactory);
         }
 
@@ -1313,7 +1313,7 @@ namespace Microsoft.AspNetCore.Antiforgery.Internal
             return builder.BuildServiceProvider();
         }
 
-        private HttpContext GetHttpContext(IAntiforgeryFeature antiforgeryFeature = null)
+        private HttpContext GetHttpContext(IAntiforgeryFeature? antiforgeryFeature = null)
         {
             var httpContext = new DefaultHttpContext();
             antiforgeryFeature = antiforgeryFeature ?? new AntiforgeryFeature();
@@ -1388,7 +1388,7 @@ namespace Microsoft.AspNetCore.Antiforgery.Internal
             AntiforgeryOptions options,
             bool useOldCookie = false,
             bool isOldCookieValid = true,
-            IAntiforgeryFeature antiforgeryFeature = null)
+            IAntiforgeryFeature? antiforgeryFeature = null)
         {
             // Arrange
             var httpContext = GetHttpContext(antiforgeryFeature);
@@ -1445,32 +1445,32 @@ namespace Microsoft.AspNetCore.Antiforgery.Internal
 
         private class TestTokenSet
         {
-            public AntiforgeryToken RequestToken { get; set; }
+            public AntiforgeryToken RequestToken { get; set; } = default!;
 
-            public string FormTokenString { get; set; }
+            public string FormTokenString { get; set; } = default!;
 
-            public AntiforgeryToken OldCookieToken { get; set; }
+            public AntiforgeryToken OldCookieToken { get; set; } = default!;
 
-            public string OldCookieTokenString { get; set; }
+            public string OldCookieTokenString { get; set; } = default!;
 
-            public AntiforgeryToken NewCookieToken { get; set; }
+            public AntiforgeryToken NewCookieToken { get; set; } = default!;
 
-            public string NewCookieTokenString { get; set; }
+            public string NewCookieTokenString { get; set; } = default!;
         }
 
         private class AntiforgeryMockContext
         {
-            public AntiforgeryOptions Options { get; set; }
+            public AntiforgeryOptions Options { get; set; } = default!;
 
-            public TestTokenSet TestTokenSet { get; set; }
+            public TestTokenSet TestTokenSet { get; set; } = default!;
 
-            public HttpContext HttpContext { get; set; }
+            public HttpContext HttpContext { get; set; } = default!;
 
-            public Mock<IAntiforgeryTokenGenerator> TokenGenerator { get; set; }
+            public Mock<IAntiforgeryTokenGenerator> TokenGenerator { get; set; } = default!;
 
-            public Mock<IAntiforgeryTokenStore> TokenStore { get; set; }
+            public Mock<IAntiforgeryTokenStore> TokenStore { get; set; } = default!;
 
-            public Mock<IAntiforgeryTokenSerializer> TokenSerializer { get; set; }
+            public Mock<IAntiforgeryTokenSerializer> TokenSerializer { get; set; } = default!;
         }
 
         private class TestOptionsManager : IOptions<AntiforgeryOptions>
diff --git a/src/Antiforgery/test/DefaultAntiforgeryTokenGeneratorTest.cs b/src/Antiforgery/test/DefaultAntiforgeryTokenGeneratorTest.cs
index 3df264d48d..39f8d4ac10 100644
--- a/src/Antiforgery/test/DefaultAntiforgeryTokenGeneratorTest.cs
+++ b/src/Antiforgery/test/DefaultAntiforgeryTokenGeneratorTest.cs
@@ -1,6 +1,7 @@
 // Copyright (c) .NET Foundation. All rights reserved.
 // Licensed under the Apache License, Version 2.0. See License.txt in the project root for license information.
 
+#nullable disable
 using System;
 using System.Security.Claims;
 using System.Security.Cryptography;
@@ -621,3 +622,4 @@ namespace Microsoft.AspNetCore.Antiforgery.Internal
         }
     }
 }
+#nullable restore
diff --git a/src/Antiforgery/test/DefaultAntiforgeryTokenStoreTest.cs b/src/Antiforgery/test/DefaultAntiforgeryTokenStoreTest.cs
index 494b91c540..d205f8efc2 100644
--- a/src/Antiforgery/test/DefaultAntiforgeryTokenStoreTest.cs
+++ b/src/Antiforgery/test/DefaultAntiforgeryTokenStoreTest.cs
@@ -282,7 +282,7 @@ namespace Microsoft.AspNetCore.Antiforgery.Internal
             Assert.NotNull(cookies);
             Assert.Equal(_cookieName, cookies.Key);
             Assert.Equal("serialized-value", cookies.Value);
-            Assert.True(cookies.Options.HttpOnly);
+            Assert.True(cookies.Options!.HttpOnly);
             Assert.Equal(defaultCookieSecureValue, cookies.Options.Secure);
         }
 
@@ -321,7 +321,7 @@ namespace Microsoft.AspNetCore.Antiforgery.Internal
             Assert.NotNull(cookies);
             Assert.Equal(_cookieName, cookies.Key);
             Assert.Equal("serialized-value", cookies.Value);
-            Assert.True(cookies.Options.HttpOnly);
+            Assert.True(cookies.Options!.HttpOnly);
             Assert.Equal(expectedCookiePath, cookies.Options.Path);
         }
 
@@ -361,7 +361,7 @@ namespace Microsoft.AspNetCore.Antiforgery.Internal
             Assert.NotNull(cookies);
             Assert.Equal(_cookieName, cookies.Key);
             Assert.Equal("serialized-value", cookies.Value);
-            Assert.True(cookies.Options.HttpOnly);
+            Assert.True(cookies.Options!.HttpOnly);
             Assert.Equal(expectedCookiePath, cookies.Options.Path);
         }
 
@@ -400,7 +400,7 @@ namespace Microsoft.AspNetCore.Antiforgery.Internal
             Assert.NotNull(cookies);
             Assert.Equal(_cookieName, cookies.Key);
             Assert.Equal("serialized-value", cookies.Value);
-            Assert.True(cookies.Options.HttpOnly);
+            Assert.True(cookies.Options!.HttpOnly);
             Assert.Equal("/vdir1", cookies.Options.Path);
             Assert.Equal(expectedCookieDomain, cookies.Options.Domain);
         }
@@ -421,9 +421,9 @@ namespace Microsoft.AspNetCore.Antiforgery.Internal
 
         private class MockResponseCookieCollection : IResponseCookies
         {
-            public string Key { get; set; }
-            public string Value { get; set; }
-            public CookieOptions Options { get; set; }
+            public string? Key { get; set; }
+            public string? Value { get; set; }
+            public CookieOptions? Options { get; set; }
             public int Count { get; set; }
 
             public void Append(string key, string value, CookieOptions options)
diff --git a/src/Antiforgery/test/DefaultClaimUidExtractorTest.cs b/src/Antiforgery/test/DefaultClaimUidExtractorTest.cs
index 67d690a83a..2a9b994d77 100644
--- a/src/Antiforgery/test/DefaultClaimUidExtractorTest.cs
+++ b/src/Antiforgery/test/DefaultClaimUidExtractorTest.cs
@@ -65,7 +65,7 @@ namespace Microsoft.AspNetCore.Antiforgery.Internal
             var claimsIdentity = (ClaimsIdentity)identity;
 
             // Act
-            var identiferParameters = DefaultClaimUidExtractor.GetUniqueIdentifierParameters(new ClaimsIdentity[] { claimsIdentity })
+            var identiferParameters = DefaultClaimUidExtractor.GetUniqueIdentifierParameters(new ClaimsIdentity[] { claimsIdentity })!
                                                               .ToArray();
             var claims = claimsIdentity.Claims.ToList();
             claims.Sort((a, b) => string.Compare(a.Type, b.Type, StringComparison.Ordinal));
@@ -258,4 +258,4 @@ namespace Microsoft.AspNetCore.Antiforgery.Internal
             }, uniqueIdentifierParameters);
         }
     }
-}
\ No newline at end of file
+}
diff --git a/src/Antiforgery/test/Microsoft.AspNetCore.Antiforgery.Test.csproj b/src/Antiforgery/test/Microsoft.AspNetCore.Antiforgery.Test.csproj
index d7654d288d..1dceca09be 100644
--- a/src/Antiforgery/test/Microsoft.AspNetCore.Antiforgery.Test.csproj
+++ b/src/Antiforgery/test/Microsoft.AspNetCore.Antiforgery.Test.csproj
@@ -2,6 +2,7 @@
 
   <PropertyGroup>
     <TargetFramework>$(DefaultNetCoreTargetFramework)</TargetFramework>
+    <Nullable>enable</Nullable>
   </PropertyGroup>
 
   <ItemGroup>