diff --git a/src/System.Net.Http/CFContentStream.cs b/src/System.Net.Http/CFContentStream.cs
index 4e4985cac8dc..b2acefdbcd9b 100644
--- a/src/System.Net.Http/CFContentStream.cs
+++ b/src/System.Net.Http/CFContentStream.cs
@@ -35,22 +35,21 @@
 using CFNetwork;
 using CoreFoundation;
 
-// Disable until we get around to enable + fix any issues.
-#nullable disable
+#nullable enable
 
 namespace System.Net.Http {
 	class BufferData {
-		public byte [] Buffer;
+		public required byte [] Buffer;
 		public int Length;
 	}
 
 	class CFContentStream : HttpContent {
 		readonly CFHTTPStream http_stream;
-		BufferData data;
+		BufferData? data;
 		Mutex data_mutex;
 		AutoResetEvent data_event;
 		AutoResetEvent data_read_event;
-		ExceptionDispatchInfo http_exception;
+		ExceptionDispatchInfo? http_exception;
 
 		// The requirements are:
 		// * We must read at least one byte from the stream every time
@@ -83,13 +82,18 @@ public CFContentStream (CFHTTPStream stream)
 			data_mutex = new Mutex ();
 		}
 
-		void HandleErrorEvent (object sender, CFStream.StreamEventArgs e)
+		void HandleErrorEvent (object? sender, CFStream.StreamEventArgs e)
 		{
+			if (sender is null)
+				return;
 			var gotMutex = data_mutex.WaitOne ();
 			if (gotMutex) {
 				var stream = (CFHTTPStream) sender;
-				if (e.EventType == CFStreamEventType.ErrorOccurred)
-					Volatile.Write (ref http_exception, ExceptionDispatchInfo.Capture (stream.GetError ()));
+				if (e.EventType == CFStreamEventType.ErrorOccurred) {
+					var error = stream.GetError ();
+					if (error is not null)
+						Volatile.Write (ref http_exception, ExceptionDispatchInfo.Capture (error));
+				}
 				data_mutex.ReleaseMutex ();
 			}
 		}
@@ -99,7 +103,8 @@ public void ReadStreamData ()
 			data_read_event.WaitOne (); // make sure there's no pending data.
 
 			data_mutex.WaitOne ();
-			data.Length = (int) http_stream.Read (data.Buffer, 0, data.Buffer.Length);
+			if (data is not null)
+				data.Length = (int) http_stream.Read (data.Buffer, 0, data.Buffer.Length);
 			data_mutex.ReleaseMutex ();
 
 			data_event.Set ();
@@ -117,7 +122,7 @@ public void Close ()
 			data_event.Set ();
 		}
 
-		protected override async Task SerializeToStreamAsync (Stream stream, TransportContext context)
+		protected override async Task SerializeToStreamAsync (Stream stream, TransportContext? context)
 		{
 			while (data_event.WaitOne ()) {
 				data_mutex.WaitOne ();
diff --git a/src/System.Net.Http/CFNetworkHandler.cs b/src/System.Net.Http/CFNetworkHandler.cs
index fbe5115091ce..ca3c03af3bda 100644
--- a/src/System.Net.Http/CFNetworkHandler.cs
+++ b/src/System.Net.Http/CFNetworkHandler.cs
@@ -37,8 +37,7 @@
 using CoreFoundation;
 using CF = CoreFoundation;
 
-// Disable until we get around to enable + fix any issues.
-#nullable disable
+#nullable enable
 
 namespace System.Net.Http {
 	/// <summary>To be added.</summary>
@@ -53,10 +52,10 @@ namespace System.Net.Http {
 	[ObsoletedOSPlatform ("tvos", "Use 'NSUrlSessionHandler' instead.")]
 	public class CFNetworkHandler : HttpMessageHandler {
 		class StreamBucket {
-			public TaskCompletionSource<HttpResponseMessage> Response;
-			public HttpRequestMessage Request;
+			public required TaskCompletionSource<HttpResponseMessage> Response;
+			public required HttpRequestMessage Request;
 			public CancellationTokenRegistration CancellationTokenRegistration;
-			public CFContentStream ContentStream;
+			public CFContentStream? ContentStream;
 			public bool StreamCanBeDisposed;
 
 			public void Close ()
@@ -92,7 +91,7 @@ public void Close ()
 		bool allowAutoRedirect;
 		bool sentRequest;
 		bool useSystemProxy;
-		CookieContainer cookies;
+		CookieContainer? cookies;
 
 		Dictionary<IntPtr, StreamBucket> streamBuckets;
 
@@ -165,7 +164,8 @@ protected override void Dispose (bool disposing)
 
 		CFHTTPMessage CreateWebRequestAsync (HttpRequestMessage request)
 		{
-			var req = CFHTTPMessage.CreateRequest (request.RequestUri, request.Method.Method, request.Version);
+			var requestUri = request.RequestUri ?? throw new InvalidOperationException ("The request URI must not be null.");
+			var req = CFHTTPMessage.CreateRequest (requestUri, request.Method.Method, request.Version);
 
 			// TODO:
 			/*
@@ -186,7 +186,7 @@ CFHTTPMessage CreateWebRequestAsync (HttpRequestMessage request)
 						}
 			*/
 			if (cookies is not null) {
-				string cookieHeader = cookies.GetCookieHeader (request.RequestUri);
+				string cookieHeader = cookies.GetCookieHeader (requestUri);
 				if (cookieHeader != "")
 					req.SetHeaderFieldValue ("Cookie", cookieHeader);
 			}
@@ -234,7 +234,7 @@ internal async Task<HttpResponseMessage> SendAsync (HttpRequestMessage request,
 
 			if (useSystemProxy) {
 				var proxies = CF.CFNetwork.GetSystemProxySettings ();
-				if (proxies.HTTPEnable) {
+				if (proxies is not null && proxies.HTTPEnable) {
 					stream.SetProxy (proxies);
 				}
 			}
@@ -268,8 +268,7 @@ internal async Task<HttpResponseMessage> SendAsync (HttpRequestMessage request,
 			stream.Open ();
 
 			bucket.CancellationTokenRegistration = cancellationToken.Register (() => {
-				StreamBucket bucket2;
-				if (!streamBuckets.TryGetValue (stream.Handle, out bucket2))
+				if (!streamBuckets.TryGetValue (stream.Handle, out var bucket2))
 					return;
 
 				bucket2.Response.TrySetCanceled ();
@@ -305,21 +304,27 @@ static bool IsRedirect (HttpStatusCode status)
 				status == HttpStatusCode.RedirectKeepVerb; // 307
 		}
 
-		void HandleErrorEvent (object sender, CFStream.StreamEventArgs e)
+		void HandleErrorEvent (object? sender, CFStream.StreamEventArgs e)
 		{
+			if (sender is null)
+				return;
 			var stream = (CFHTTPStream) sender;
 
-			StreamBucket bucket;
-			if (!streamBuckets.TryGetValue (stream.Handle, out bucket))
+			if (!streamBuckets.TryGetValue (stream.Handle, out var bucket))
 				return;
 
 			var ex = stream.GetError ();
-			bucket.Response.TrySetException (new HttpRequestException (ex.FailureReason, ex));
+			if (ex is not null)
+				bucket.Response.TrySetException (new HttpRequestException (ex.FailureReason, ex));
+			else
+				bucket.Response.TrySetException (new HttpRequestException ("Unknown error"));
 			CloseStream (stream);
 		}
 
-		void HandleClosedEvent (object sender, CFStream.StreamEventArgs e)
+		void HandleClosedEvent (object? sender, CFStream.StreamEventArgs e)
 		{
+			if (sender is null)
+				return;
 			var stream = (CFHTTPStream) sender;
 			// might not have been called (e.g. no data) but initialize critical data
 			HandleHasBytesAvailableEvent (sender, e);
@@ -339,21 +344,25 @@ void CloseStream (CFHTTPStream stream)
 			stream.Close ();
 		}
 
-		void HandleHasBytesAvailableEvent (object sender, CFStream.StreamEventArgs e)
+		void HandleHasBytesAvailableEvent (object? sender, CFStream.StreamEventArgs e)
 		{
+			if (sender is null)
+				return;
 			var stream = (CFHTTPStream) sender;
 
-			StreamBucket bucket;
-			if (!streamBuckets.TryGetValue (stream.Handle, out bucket))
+			if (!streamBuckets.TryGetValue (stream.Handle, out var bucket))
 				return;
 
 			if (bucket.Response.Task.IsCompleted) {
-				bucket.ContentStream.ReadStreamData ();
+				bucket.ContentStream?.ReadStreamData ();
 				return;
 			}
 
 			var header = stream.GetResponseHeader ();
 
+			if (header is null)
+				throw new InvalidOperationException ("Failed to get response header.");
+
 			// Is this possible?
 			if (!header.IsHeaderComplete)
 				throw new NotImplementedException ();
@@ -372,14 +381,16 @@ void HandleHasBytesAvailableEvent (object sender, CFStream.StreamEventArgs e)
 						continue;
 
 					var key = entry.Key.ToString ();
-					var value = entry.Value is null ? string.Empty : entry.Value.ToString ();
+					if (key is null)
+						continue;
+					var value = entry.Value is null ? string.Empty : entry.Value.ToString () ?? string.Empty;
 					HttpHeaders item_headers;
 					if (IsContentHeader (key)) {
 						item_headers = response_msg.Content.Headers;
 					} else {
 						item_headers = response_msg.Headers;
 
-						if (cookies is not null && (key == "Set-Cookie" || key == "Set-Cookie2"))
+						if (cookies is not null && (key == "Set-Cookie" || key == "Set-Cookie2") && bucket.Request.RequestUri is not null)
 							AddCookie (value, bucket.Request.RequestUri, key);
 					}
 
@@ -391,14 +402,14 @@ void HandleHasBytesAvailableEvent (object sender, CFStream.StreamEventArgs e)
 			if (!bucket.Response.Task.IsCanceled) {
 				bucket.Response.TrySetResult (response_msg);
 
-				bucket.ContentStream.ReadStreamData ();
+				bucket.ContentStream?.ReadStreamData ();
 			}
 		}
 
 		void AddCookie (string value, Uri uri, string header)
 		{
 			try {
-				cookies.SetCookies (uri, value);
+				cookies?.SetCookies (uri, value);
 			} catch {
 			}
 		}
diff --git a/tests/cecil-tests/ObsoleteTest.cs b/tests/cecil-tests/ObsoleteTest.cs
index a562ec57c284..6f77488294aa 100644
--- a/tests/cecil-tests/ObsoleteTest.cs
+++ b/tests/cecil-tests/ObsoleteTest.cs
@@ -44,6 +44,10 @@ public void GetAllObsoletedThings (AssemblyInfo info)
 
 		bool FilterMember (ICustomAttributeProvider provider)
 		{
+			// We don't care about APIs that aren't public
+			if (provider is MemberReference mr && !mr.IsPubliclyVisible ())
+				return false;
+
 			// If an API isn't obsolete, it's not under scrutiny from this test.
 			if (!provider.IsObsolete ())
 				return false;